3301, 8194 hks
While checking receipts at The Hog Cafe, it was determined that the average amount spent on food per table was $21.50 with a standard deviation of $2.22. If we can assume that the amount of money spent was normally distributed, what is the probability that the average of 8 checks is between $20 and $23?
0.9438
According to the Empirical Rule, approximately what percentage of observations are between 2 standard deviations above the mean and 2 standard deviations below the mean in a normal distribution?
95%
Angioplasty is a surgical procedure to restore blood flow through narrow or blocked arteries. More than a million heart patients undergo this procedure every year. A recent study of 1,256 heart patients assessed the benefits of angioplasty. In this study, all patients had substantial blockage of their arteries and were being treated with medication such as aspirin and beta-blockers. The researchers randomly assigned half of the patients to receive angioplasty. The other half did not receive the surgical procedure. After 10 years, the researchers compared the heart attack rates for the two groups. For the individuals who received the surgical procedure, the researchers also tested to see if there was a difference in resting blood pressure before and after receiving the surgery. If the surgery effectively reduced blockage, then the researchers would expect to see a significant drop in blood pressure following surgery. If appropriate, aassume equal variances. What type of statistical test should the researchers use to analyze this data?
Paired t-test for means
Which type of graph would best represent how student time is spent during the day between homework, chores, school, and relaxing?
Pie Chart
An consultant came up with a new plan to increase productivity at your office. When you compared those who followed the plan to those in a different office who did not adopt the plan, your p-value was .85. Is this plan helpful?
Probably
A polling company finds that 60% of Democrats give a 'favorable' rating for a senator and 52% of Republicans give a 'favorable' rating for the same senator. What should the company use if they want to know if this is a 'statistically significant' finding?
Two proportions z-test
Consider the following hypotheses that relate to the medical field: Ho: A person is free of disease Ha: A person has disease
Type 1 error: a false positive Type 2 error: NOT: a false positive
There is no fire, but the smoke detector goes off. What type of error is this?
Type I error
There is a fire, but the smoke detector doesn't go off. What type of error is this?
Type II error
In hypothesis testing, we use a _________ to make an inference about a _________.
sample statistic; population parameter
What is the probability that a randomly selected student will be paying between $15,000 and $20,000 a year for tuition at Sunshine State University?
.6821
What is the probability that a randomly selected student will be paying between $15,000 and $20,000 a year for tuition at Sunshine State University? 3. Does the true population mean ($18,695) fall within the estimated 95 percent confidence interval calculated based on the 25 sample students?
.6821 $17,106, $18,802 3.Yes
Anderson, an undergraduate student at Sunshine State University, told his parents that his annual tuition will cost $23,185. What is the probability that Anderson's annual cost of tuition is less than he claims?
.9812
Managers at Snapchat are concerned that employee turnover will increase after the company goes public in April 2017. They are considering options to improve employee retention but in the meantime want to get an idea of employees' turnover intentions before April 2017 to serve as a baseline measure. Seventy-five (75) employees were randomly selected and asked to respond to the following question: "Do you plan to search for a job at another company within the next 6 months?" Employees chose from the following response options: "Yes, Definitely," "Maybe," or "No, Definitely Not." 11 employees responded that they would definitely plan to search for a job at another company within the next six months. What are the upper and lower level confidence limits for employee turnover intentions, at the 95% confidence interval?
0.0666, 0.22673
Suppose the mathematics SAT scores are normally distributed with a mean of 500 and a standard deviation of 100, and the ACT scores are normally distributed with a mean of 18 and a standard deviation of 6. If a school only accepts students with mathematics SAT scores in the top 20 percent, what is the approximate minimum mathematics SAT that would be acceptable for that school.
584 23
Suppose the mathematics SAT scores are normally distributed with a mean of 500 and a standard deviation of 100, and the ACT scores are normally distributed with a mean of 18 and a standard deviation of 6. If a school only accepts students with ACT scores in the top 10 percent, what is the approximate minimum ACT score that would be acceptable for that school.
628 26
The table below shows data on a subsample of participants in the 7th examination of the Framingham Offspring Study.
Which of the following is the 99% confidence level for Total Serum Cholesterol 171.59, 233.01
Does the true population mean ($18,695) fall within the estimated 95 percent confidence interval calculated based on the 25 sample students?
Yes
For which of the following scenarios would a matched pairs test be most appropriate?
You have annual data on the returns of 2 different mutual funds for each of the past 40 calendar years and want to know which fund has the higher annual return
A university interested in tracking its honors program believes that the proportion of graduates with a GPA of 3.00 or below is less than 0.20. In a sample of 200 graduates, 30 students have a GPA of 3.00 or below. The value of the test statistic and its associated p-value are
Z = -1.77
The owner of a large car dealership believes that the financial crisis decreased the number of customers visiting her dealership. The dealership has historically had 800 customers per day. The owner takes a sample of 100 days and finds the average number of customers visiting the dealership per day was 750. Assume that the population standard deviation is 350. At a 5% significance level, the critical value(s) is(are)
Z= -1.645
A Type I error occurs when
a null hypothesis is rejected but should not be rejected reject the null hypothesis when it is actually true
Entry to a the University of Arkansas is determined by a national test. The scores on this test are normally distributed with a mean of 500 and a standard deviation of 100. Jeff wants to be admitted and he knows that he must score better than at least 70% of the students who took the test. Tom takes the test and scores 585. Will he be admitted to this university?
yes
The owner of a large car dealership believes that the financial crisis decreased the number of customers visiting her dealership. The dealership has historically had 800 customers per day. The owner takes a sample of 100 days and finds the average number of customers visiting the dealership per day was 750. Assume that the population standard deviation is 350. The value of the test statistic is
z = -1.429
The pie chart represents a monthly expenditure of a household that totals $800:
$160
A sample of 25 students shows that the mean annual tuition cost is $17,954. Assuming that the sample is from a normal population, what is the 95% confidence interval for the true population mean?
$17,106, $18,802
In an unfortunate accident, Sunshine State University lost all of their tuition cost records. To determine the annual cost of tuition, administrators sampled 49 undergraduate students and found that the annual cost of tuition is normally distributed with a mean of $19,354 and a standard deviation of $4,579. What is the estimated interval for at a 90 percent confidence level?
$18,257, $20,451
The administration at Sunshine State University is trying to lower the cost of tuition for those students paying the highest annual tuition. If the university is providing financial support to students paying more in annual tuition than 95% of the students at Sunshine State University, what would be the cut-off?
$22,253
Robert received a letter from Sunshine State University informing him that his annual cost of tuition is 2.3 standard deviations above the mean annual cost of tuition for all students at Sunshine State University. About how much is Robert paying for his annual tuition?
$23,670
The distribution of annual profit at a chain of stores was approximately normal with mean = $66,000 and standard deviation = $21,000. The executives conducted an audit of the stores with the lowest 20% of profits. What is closest to the maximum annual profit at a store where the executives conducted an audit? Round to the nearest thousand dollar.
$48,000
Jason pays $16,845 in tuition to attend Sunshine State University. What is the probability that a randomly selected student at Sunshine State University will pay less for tuition than Jason?
.1949
It has been claimed that beetroot juice reduces blood pressure. Researchers investigated the claim using 3 different research designs: 1. A group of randomly sampled individuals are randomly assigned to 2 groups. One group is given beetroot juice everyday for 4 weeks. The other group is given red drink everyday fro 4 weeks. After 4 weeks, the average blood pressure is calculated for both groups. 2. The blood pressure for a group of randomly sampled individuals was measured before the study. Each individual was given beetroot juice everyday for 4 weeks. The blood pressure for each individual was measured again at the end of the study. 3. A group of randomly sampled individuals with known high blood pressure was given beetroot juice everyday for 4 weeks. After 4 weeks, their blood pressure was measured and averaged. The average was compared to 140/90 with is the threshold for high blood pressure. Which test should be used in each of the above situations?
1 - Independent two-sample t-test 2 - Matched Pairs t-test 3 - One Sample t-test
The time spent by a teacher at work in the holidays is normally distributed with a mean of 20 hours and a standard deviation of 5 hours. What amount of time do the bottom 20% of teachers work?
15.79
The time spent by a teacher at work in the holidays is normally distributed with a mean of 20 hours and a standard deviation of 5 hours. What times do the middle 40% of teachers work between?
17.38, 22.62
The distribution of average wait times in drive-through restaurant lines in one town was approximately normal with mean = 185 seconds and standard deviation = 11 seconds. Jen only likes to use the drive-through for restaurants where the average wait time is in the bottom 10% for that town. What is the maximum average wait time for restaurants where Jen likes to use the drive-through? Round to the nearest whole second.
171 seconds
Vermont-based Green Mountain Coffee Roasters dominates the market for single-serve coffee in the United States, with its subsidiary Keurig accounting for approximately 70% of sales ("Rivals Try to Loosen Keurig's Grip on Single-Serve Coffee Market," Chicago Tribune, February 26, 2011). But Keurig's patent on K-cups, the plastic pods used to brew the coffee, is expected to expire in 2012, allowing other companies to better compete. Suppose a potential competitor has been conducting blind taste tests on its blend and finds that 47% of consumers strongly prefer its French Roast to that of Green Mountain Coffee Roasters. After tweaking its recipe, the competitor conducts a test with 144 tasters, of which 72 prefer its blend. The competitor claims that its new blend is preferred by more than 47% of consumers to Green Mountain Coffee Roasters' French Roast. What critical value should be used to test this claim at the 1% significance level?
2.326
Use the pie chart/circle graph to find the best answer to the question
22 hours 8 hours
Find the mode(s) of the dataset: 18, 36, 24, 36, 30, and 36
36
The Welcher Adult Intelligence Test Scale is composed of a number of subtests. On one subtest, the raw scores have a mean of 35 and a standard deviation of 6. Assuming these raw scores form a normal distribution. What number approximately separates the lower 90% of the distribution?
43
A financial analyst with Bank of America collected data from the automobile industry for a specific type of car, the Ford Mustang. She collected data for total sales ($), display floor space (square meters), competitor advertising expenditures ($), and advertised price ($). Assume α=.05.
75.9% of the variance in sales is explained by the independent variables Floor space is the only independent variable that is statistically significant FloorSpace has a positive slope statistically different from 0. $1,084,107
Scores on an exam in Dr. B's class were normally distributed with a mean of 80 and a standard deviation of 10. Fred's score on the exam exceeded 95% of all scores in the class. What was Fred's approximate score on the test?
96
According to the Empirical Rule, approximately what percentage of observations are between 3 standard deviations above the mean and 3 standard deviations below the mean in a normal distribution?
99.7%
This year, Josephine paid $25,148 for her tuition. About what percentage of students pay less in tuition than Josephine?
99.86%
Based on the information provided and your calculations, what can you conclude about Anderson's statement to his parents regarding his cost of tuition at Sunshine State University?
Anderson may not have told his parents the truth as it is unlikely that Anderson's tuition costs that much
The scatter plot below shows the average traffic volume and average vehicle speed on a certain freeway for 50 days in 1999:
As traffic volume increases, vehicle speed decreases
In each of the following, the p-value and significance level a are given for a test of hypothesis. Which pair of values warrants a rejection of the null hypothesis?
Choose the answer with P lower than A
The high electrical conductivity of copper is an important design factor that helps improve the energy efficiency of electric motors. This is important because motors and motor-driven systems are significant consumers of electricity, accounting for 43% - 46% of all global electricity consumption and 69% of all electricity used by industry. Inefficient motors waste electrical energy and are indirect contributors to greenhouse gas emissions. ElectroSpark, Inc. has been developing a new copper die-cast rotor technology specifically for premium efficiency motors, replacing the standard aluminum rotor. There are multiple reasons for doing so, including the possibility that the motor will consume less energy. They designed an experiment to test their idea in a common ¾ Horse power (HP) motor that is normally manufactured with an aluminum rotor. They designed a copper rotor that fit in their ¾ HP motor housing and ran a production line for a day producing the motors. They randomly selected 20 copper-rotor motors from that output and 20 aluminum-rotor motors produced from the same line the day before. These 40 motors were all run for 8 hours a day for 30 days and the energy consumed was measured in total Kilowatt Hours (example data below, using alpha=.05):
Dependent variable: Energy use in Kilowatt hours H0: μ_copper - μ_aluminum ≥ 0; H1: μ_copper - μ_aluminum < 0 Reject H0 at the 0.05 level of significance
The average time in years to get an undergraduate degree in computer science was compared for men and women. Random samples of 100 male computer science majors and 100 female computer science majors were taken. Choose the appropriate parameter(s) for this situation.
Difference between two population means
A growing concern among fans and owners is the amount of time to complete a major league baseball game. To assess the extent of the problem, a statistician recorded the amount of time (in minutes) to complete a random sample of games 5 years ago and another random sample of games played this year. The average amount of time 5 years ago to complete a game was 176.85 minutes with a standard deviation of 30.78 minutes. The average amount of time this year to complete a game was 188.35 minutes with a standard deviation of 25.16 minutes. Can we conclude that games take longer to complete this year than 5 years ago (level of significance = .05)?
F-test and then t-Test assuming equal variance H0: μ 5 years ago- μ This year≥ 0; H1: μ 5 years ago- μ This year < 0
Upstart roofing shingle manufacturer Acme Shingles Inc. wants to challenge the market leaders in this category. It has developed a thermoplastic adhesive that it believes is superior in attaching granules to the shingle paper in their new shingle appropriately called "EverDry." Before launching an advertising campaign, Acme's product managers want to make sure that their new shingle will last longer than competitor's product, "DuraLast." In accelerated-life testing, a lifetime of normal use is simulated by repeatedly scraping the shingle with a brush for a short period of time. The granules that fall off are collected and weighed (in grams). Shingles that experience low amounts of granule loss are expected to last longer in normal use than shingles that experience high amounts of granule loss. Product managers selected 60 different EverDry shingles from different production runs in Acme's plant. They sent college interns out to a number of building supply houses to purchase random samples of Duralast, the competitor's product. After the accelerated-life testing on their two testing machines, they recorded the grams lost for each product and ran the following analyses at alpha =.05, not all of which are relevant.
H0: (μeverdry - μduralast) ≥ 0; H1: (μeverdry - μduralast) < 0 Reject H0 at the 0.05 level of significance Conclude that the test results, although statistically significant, suggest further study before significant investments can be made in advertising. Non-experimental design False
A researcher wants to determine whether MBA students are more risk seeking than undergraduates in an investment context. To explore this hypothesis, a study was conducted to examine the riskiness of choices made in stock selection. Undergraduate and MBA students were presented with a list of different mutual funds that, based on their past performance, could be identified as either high risk or low risk investments. Suppose that 100 undergraduate students and 100 MBA students were selected and asked where they would be most likely to invest a $1,000 tax refund. 27 of the undergraduates said that they would invest in a high-risk mutual fund, whereas 82 of the MBA students reported that they would invest in a low risk fund. Which is the researchers' hypothesis?
H0: MBA - undergrad = 0, H1: MBA - undergrad > 0
The University of Arkansas surveyed Human Resources (HR) executives from 45 companies that employed students who recently graduated from the U of A. The HR executives indicated that they feel that the current generation of college students feels more entitled (i.e., deserving of special treatment at work) than any previous generation. Dr. Iam Worthy, a professor of Psychology at the U of A, thinks that recent college graduates are no more entitled than those from previous generations and that what employers are observing is that recent graduates are actually living up to their employers' expectations by becoming more entitled once they are on the job. To test this belief, Dr. Worthy identified a cohort of 100 college seniors who are planning to start working immediately after graduation. Dr. Worthy surveys this cohort 2 months before graduation and asks each member to report their sense of entitlement on a 7-point ordinal scale, with responses ranging from 1 (not at all entitled) to 7 (extremely entitled), such that higher numbers indicate greater levels of entitlement. Two months after each member of the cohort has started his or her job, Dr. Worthy asks each member of the cohort to respond to the same question. Do the data support Dr. Worthy's belief?
H0: µD(before graduation-after graduation) ≥ 0 H1: µD(before graduation-after graduation) < 0 Do not reject the null hypothesis; conclude that U of A graduates do not become more entitled once they start work t-Test: paired two sample for means pre-test, post-test quasi-experimental study 1
You are a manufacturer of an MP3 player. In September, before the major shopping season begins, you wanted to know if a 10% reduction in price would be enough to increase sales of your MP3 player, which hasn't been selling well lately. If so, you plan to launch a promotion on Black Friday. You randomly select 7 retail stores to sell your MP3 player at a reduced price for a month. You compare the units sold to another 7 randomly selected stores that sold the MP3 player at the regular price. You can't afford to lower the price unless you are positive the reduction will increase sales so you choose alpha = 0.01.
H0: μRegularprice- μ Reducedprice ≥ 0; HA: μRegularprice- μ Reducedprice < 0 The F-Test for two variances, then the t-Test assuming equal variance Although the average units sold during the month (x-bar= 125.86) on the reduced priced MP3 player is higher than the regularly priced MP3 player (x-bar=117.71), the difference is not significant, therefore you decide to not alter the MP3 price. 1
Scientists believe that world population growth will outpace normal increases in world food production in the world food system by 2040. Accordingly, many agricultural companies are exploring how to improve yields through improved fertilizer formulations. The Grofast Industrial Ag Company is conducting a test of their new fertilizer product for corn which normally yields an average of 40,000 lbs./acre. For this study, they randomly selected 20 plots from their 8,000 acres of seedbeds. They intend to plant identical plots of a hybrid corn variety in each lot. In half the lots they will fertilize with the company's current fertilizer blend. In the other half they intend to fertilize with the new blend of fertilizer. They want to hold all other conditions the same. Using a coin toss, they assign the lots for the old and new fertilizer and recorded the average corn yield (in thousands of lbs./acre) for each of the plots at season's end.
H0: μnew- μold ≤ 0: H1: μnew - μold > 0 Both a and b a. Reject the null hypothesis at the 0.10 level of significance b. Reject the null hypothesis at the 0.05 level of significance Based on the statistical evidence, Grofast can anticipate the new fertilizer product will aid in the fight against hunger. interval/ratio True experiment
Pamela, and educational psychologist, is interested in assessing whether there are differences in how college students with different majors might respond to an ethical dilemma. To this end, she performed a study in which undergraduate marketing and finance majors were asked what they would do if they found a $100 bill in a Walton College of Business classroom. Specifically, would they turn in the $100 bill to the Walton College of Business lost and found? Of the 69 marketing majors who were randomly sampled, 52 said yes and of the 131 finance majors who were randomly sampled, 120 said yes (assume alpha equals .05).
H0: π marketing - π finance = 0 HA: π marketing - π finance ≠ 0 Reject H0; conclude that there is a difference in the proportion of marketing majors who would turn in the $100 bill relative to finance majors
In 2009, the Southeastern Conference (SEC) commissioner set a goal to have greater than 65% of athletes that are entering freshmen graduate in 6 years. In 2015, a sample of 100 entering freshmen from 2009 was taken and it was found that 70 had graduated in 6 years. Does this data provide evidence that the commissioner's graduation goal was met (α = .10)? For this scenario, which would be the proper set of hypotheses?
H0: π ≤ .65, HA:π >.65 P: 0.1469
There is a growing call for nations to control CO2 emission levels from automobiles. The National Center for Pollution Control commissioned a study to better understand what interventions could lead to decrease in usage of automobiles and thus reduced CO2 emission levels. Bill Anderson, a senior researcher of environmental science was tasked with carrying out this study and was given 3 weeks to report back with preliminary findings. Bill believed people who are fitness conscious are, on average, more likely to avoid usage of cars whenever a safe commute by walk or bike is possible. To test this belief, a survey was conducted at the University of Arkansas' Bell Engineering Center. A sample of 50 students who engage in a moderate form of exercise at least three times a week was chosen to represent the fitness conscious group. Similarly, a sample of 50 students who reported engaging in any form of physical activity less than four times a month was chosen to represent people not concerned about their fitness. Each participant was asked "If you had to travel to a place very close to your home, which mode of commute would you prefer - 1. Driving my Car, 2. Biking or Walking. The researcher tabulated the response on commute preference as Driving (coded = 1) vs. Biking/Walking (coded = 2).
H0: πFC - πNFC ≤ 0; H1: πFC - πNFC > 0 Reject the null hypothesis at an alpha level of .05 Conclude that fitness-conscious people are more likely to bike / walk compared to non-fitness conscious people. Non-experimental design
Technology has led to the rise of extreme workers who are on the job 60 hours a week or more. One of the reasons cited by employees about why they work long hours was that they loved their job because it was stimulating. Suppose that the survey of 1564 workaholics included 786 men and 778 women, and 707 men and 638 women loved their job because it is stimulating. At the 0.05 level of significance, you would like to determine whether the proportion of workaholic men who love their job because it is stimulating is greater than the proportion of women who do. Which of the following hypotheses would you want to test?
H0: πwomen - π men = 0 ; H1: πwomen - π men < 0 Non-experimental design none of the above; the correct test was not run NOT: Management's hypothesis is confirmed at alpha=.05 and alpha=.01 NOT: Management's hypothesis is confirmed at alpha=.05 Management's hypothesis is confirmed at alpha=.01
Reed Hastings, the CEO of Netflix, is thinking about raising subscription prices (again). David Wells, who serves as the chief financial officer warns that Netflix will lose money in the long run if more than 7% of current customers cancel their subscriptions as a result of the rate hike. To assess the possibility that Netflix will lose money, the marketing department surveyed 50 male and 50 female customers and matched the customers on how long they had subscribed to Netflix. Four women and five men indicated that they would drop their membership if Netflix raised its rates. Based on these results, N =100, is it likely that Netflix will lose money as a result of the rate increase?
H0: π≤ .07, Ha: π >.07 z-Test = +.67 P Value= +.25 Fail to reject the null hypothesis; conclude that it is unlikely that Netflix would lose money * Alpha to .05 instead of .10? = it goes down
Sally, a recent graduate of the University of Arkansas, accepted a position as an event coordinator for a major marketing firm. Sally's first task is to organize a convention of retailers and manufactures of private label store brands. She wants to select a city that has low hotel cost. She has narrowed her choice to Atlanta and New Orleans. She collects sample data on 25 hotels in both cities for a 5 night stay. Since there is a vast amount of historical data for hotel prices in both cities, she finds the known variance to be $125 in Atlanta and $150 in New Orleans. Can she conclude that there is a difference in hotel cost between the two cities? If there is a difference, she will use that information and select the city with the lower cost. The level of significance is .10. If appropriate, you should assume unequal variances.
H0:μAtlanta - μNew Orleans = 0 HA:μAtlanta - μNew Orleans ≠ 0 Independent variable: City (Atlanta and New Orleans) Reject H0 when in reality there is no difference in hotel prices.
The Boston public school district has had difficulty maintaining on-time bus service for its students ("A Year Later, School Buses Still Late," Boston Globe, October 5, 2011). Suppose the district develops a new bus schedule to help combat chronic lateness on a particularly woeful route. Historically, the bus service on the route has been, on average, 12 minutes late. After the schedule adjustment, the first 36 runs were an average of 8 minutes late. As a result, the Boston public school district claimed that the schedule adjustment was an improvement-students were not as late. Assume a population standard deviation for bus arrival time of 12 minutes. Develop the null and alternative hypotheses to determine whether the schedule adjustment reduced the average lateness time of 12 minutes.
Ho u>12 and Ha u<12
The owner of a large car dealership believes that the financial crisis decreased the number of customers visiting her dealership. The dealership has historically had 800 customers per day. The owner takes a sample of 100 days and finds the average number of customers visiting the dealership per day was 750. Assume that the population standard deviation is 350. In order to determine whether there has been a decrease in the average number of customers visiting the dealership daily, the appropriate hypotheses are
Ho: U > 800 and Ha: u<800
A school teacher is worried that the concentration of dangerous, cancer-causing radon gas in her classroom is greater than the safe level of 4pCi/L. The school samples the air for 36 days and finds an average concentration of 4.4pCi/L with a standard deviation of 1pCi/L. In order to test whether the average level of radon gas is greater than the safe level, the appropriate hypotheses are
Ho: u< 4 and Ha >4
Explain what the phrase "95% confident" means when we interpret a 95% CI for μ
In repeated sampling, 95% of constructed intervals would contain the value of μ In repeated sampling from the same population, 95% of similarly constructed intervals contain the value of the population mean.
Suppose we were interested in determining if there were differences in the average prices among two local supermarkets. We randomly pick six items at one supermarket and the same six items at the other supermarket. Which statistical procedure would be best to use for this study?
Independent two sample t-test
The Stevens Motor Company is developing high powered engines for use in its new sports coupe. The engineers have advertised that the maximum horsepower for the engine is 600HP. They sampled 16 engines and found the average to be 620HP (σ = 50). If the engineers sampled a larger number of engines, what would happen to the width of the confidence interval?
It would get narrower: the upper and lower confidence limits would get closer together
A colleague is conducting research on adults' job satisfaction as it relates to gender, salary, and level of control felt over the work environment. Your colleague has collected data from a random sample of adults. Salary is measured in thousands of dollars. The control over one's work environment and job satisfaction scales are measured by averaging sets of items on a 0 to 7 point scale range, with low scores representing low control and low job satisfaction and higher scores representing a greater sense of control and job satisfaction. Here are the data. She is particularly interested in the relationship between job satisfaction and the person's perceived level of control.
MODE : both 2 and 5 Average and Median: 4, 3.5
The police department tracked the number of ticket writers and number of tickets issued for the past 8 weeks. The scatter plot shows the results. Based on the scatter plot, which statement is true?
More ticket writers results in more tickets issued
A recent report claimed that Americans are retiring later in life (U.S. News & World Report, August 17, 2011). An economist wishes to determine if the mean retirement age has increased from 62. To conduct the relevant test, she takes a random sample of 38 Americans who have recently retired and computes the value of the test statistic as t= 1.92 With a = 0.05, she
NOT (rejects the null hypothesis and concludes that the mean retirement age has not increased)
Carmen and Dan work for Walmart and would like to test a new store layout to see if it improves sales for stores. They would like to move electronics to the front of the store because that section has much better store margins than other products. They select ten stores from each state and, for each state, randomly assign each store to be in either the treatment or control condition. In the treatment condition, the electronic section is to be moved to the front of the store. No changes were planned for stores in the control condition. After planning the test, Carmen and Dan are told that the stores in their test cannot move the electronics up front due to the costs of redesign. In fact, only two stores in the whole company can move the section because they are already in the process of remodeling so there would be minimal incremental costs. Carmen and Dan redo their test design to measure the sales pre remodel and post remodel to measure the impact. This is an example of a:
NOT: Non Experimental Design
A plasma TV manufacturer determines that their TV's are problem free for an average of 60 months. Assume the problem free period is normally distributed with a standard deviation of 4 months. About how many months should an extended warranty last if the company wants a TV to have a 99% chance of being problem free during the warranty period.
NOT: 67 Months
The University of Arkansas recently approved out of state tuition discounts for high school students from any state. The students must qualify by meeting certain standards in terms of GPA and standardized test scores. The goal of this new policy is to increase the geographic diversity of students from states beyond Arkansas and its border states. Historically, 90% of all new students came from Arkansas or a bordering state. Ginger, a student at the U of A, sampled 180 new students the following year and found that 157 of the new students came from Arkansas or a bordering state. Does Ginger's study provide enough evidence to indicate that this new policy is effective with a level of significance 10%? What hypothesis is being tested?
NOT: H0: π ≥ .87, HA: π < .87
A popular weekly magazine claims that fewer than 55% of voters voted for presidential candidate X. NBC news hires a polling company to conduct an independent study to verify this claim. The polling company conducted a survey of 100 randomly selected voters and found that 48 voted for candidate X. At the 5% significance level, which of the following conclusion is appropriate?
NOT: Reject the null and conclude that the magazine's claim is not valid
Brad, a professor in the Walton College of Business, has taught Data Analysis for 3 years. Historically, during that time, his average grade is 70% with a standard deviation of 5%. He is disappointed in the results of his students and decides to try different teaching methods to improve their grades. In the spring of 2016, he develops on-line videos as a supplement to his class lecture. During that semester, his average grade is 71% from a sample of 49 students. The level of significance is 2.5%. What is the correct conclusion?
NOT: Reject the null hypothesis, conclude the grades did not improve
Over the past year, Linda Money taker, the vice president for human resources at a large petroleum company has run a series of eight-week workshops aimed at increasing worker motivation and performance. To check the effectiveness of the workshop, she selected a random sample of 25 employees from the personnel files and recorded their most recent annual performance ratings, along with their ratings prior to attending the workshops. If Linda wants to examine whether or not the workshop has an impact on performance, which test should she use?
NOT: t-test for paired means
Yancy, a Walton College of Business graduate, wants to start a hot dog stand on Dickson Street. He needs to raise $15,000 for start-up supplies and equipment. He believes that in order to be successful, he would need to sell more than 300 hot dogs on average per night. He creates a survey and stands on Dickson Street asking people to state whether or not they would buy a hot dog. He notices that the demand increases significantly after midnight. Sixty people complete his survey and based on their feedback, he purchases the supplies and equipment. He opened his stand and after the first two weeks he wants to analyze his sales. He is open 5 days a week and finds the average number of hot dogs sold is 335 with a standard deviation of 50. Is he meeting his original goal to be successful? Assume a 5% level of significance for this question. What is the correct conclusion?
NOT: Fail to reject H0, he is meeting his original goal to be successful NOT: Fail to reject H0, he is not meeting his original goal to be successful
Are nursing salaries in Tampa, Florida, lower than those in Dallas Texas? Salary data provided by Salarly.com shows that staff nurses in Tampa earn less than staff nurses in Dallas. Suppose that in a follow-up study using 40 randomly selected staff nurses in Tampa and 40 randomly selected staff nurses in Dallas you collect your own data asking each staff nurse their current salary.
Non experimental A negative correlation coefficient. Large t statistic for the slope There is more than one independent variable. Small p -value for the estimated slope Failing to reject the null and claiming that Tampa nurses make the same amount as staff nurses in Dallas, when in fact Tampa nurses make less. Rejecting the null and claiming that Tampa nurses on average make less, on average, than Dallas nurses when in fact the make the same on average Either b or c depending upon the F-test b. t-Test assuming unequal variance c. t-Test assuming equal variance
Which two MONTHS appear to have the same amount of candy sold?
November & March
The amount of candy sold in December is twice the amount of candy sold in which other month?
October
Anthony was interested in the height of athletes participating in the 2012 Olympics, so he collected data on all of the athletes that participated in the Olympics. His results indicated that the average height of an Olympian was 6 feet tall with a standard deviation of 0.5 feet. The average height and standard deviation calculated by Anthony is an example of:
Population Parameters
What type of data would necessitate using a hypothesis test of the population proportion rather than a test of the population mean?
Qualitative
A researcher in the field of educational psychology is interested in the effects an open classroom has on intellectual development. In the open classroom things are much less structured than in a traditional classroom and she believes that this might affect problem-solving skills. An elementary school in her district switched to an open classroom format last year, and she is interested to see how this has impacted on the kids problem-solving skills. She obtains a random sample of 49 fourth grade children and administers a conceptual problem-solving test to them. It is known that fourth graders in traditional classes have an average score of 82 on the test. The children in this study score an average of 86 with a standard deviation of 5. Which type of statistical test should the researcher do?
T= 5.60 one sample T-test NOT: independent two sample t-test NOT: H0: straight pi MBA - straight pi undergrad = 0, H1: straight pi MBA - straight pi undergrad < 0
Many retailers are trying to figure out whether consumers care about "green" products, and if they would pay more for products that are advertised as being green. One retailer decided to conduct a consumer study in a very large major metropolitan area in which it had many stores. The retailer devised a label scheme that ranked products on a scale of 1 to 5, where 1 = least environmentally friendly and 5 = most environmentally friendly. This ranking was added to existing labels on the retailer's private brands. The retailer randomly chose 10 of their stores to sell the products with the new labeling (E-label). The retailer compared unit sales of these same products, but without the new labels (No_E-Label), at another 10 randomly selected stores in the same 10 mile radius. The retailer wanted to know whether sales would be better or worse with the new labels with no price change. If the sales were not statistically different, The retailer planned to proceed with a test that included increased price for the E-Product. The retailer decided that α = .10 for purposes of this test. Example unit sales are included in the table below.
THE QUESTION MAY BE DIFFERENT IF F IS MORE THAN .025 it's EQUAL variance The F-Test for two variances, then the t-Test assuming unequal variance The F-Test for two variances, then the t-Test assuming equal variance H0: μE-Label- μNo_E-Label = 0; HA: μE-Label - μNo_E-Label ≠ 0 NOT: Although the average units sold during the month of the E-Labeled product (11.93) is higher than the normally labeled product (10.80), the difference is not significant, therefore you decide to begin price testing. Since the average units sold during the month of the E-Labeled product (11.93) is higher than the normally labeled product (10.80), you should begin price testing.
There is a fire, and the smoke detector goes off. What type of error is this?
There is no error
There is no fire, and the smoke detector does not go off. What type of error is this?
There is no error
The value that separates a rejection region from an acceptance region is called a ___________
critical value
An educational researcher wanted to know if in-class activities significantly improved students' learning compared to traditional lecture only teaching methods. Ten students matched on GPA, Year in school, and academic major were randomly selected from the current student population. One student from each pair was randomly assigned to either the Lecture Only class or Lecture plus Group Activities class. At the end of the semester, students' final exam scores were recorded and teaching methods were compared. Which type of statistical test should the researcher do?
matched pairs t-test
The Institute of Education Sciences measures the high school dropout rate as the percentage of 16- through 24-year-olds who are not enrolled in school and have not earned a high school credential. In 2009, the high school dropout rate was 8.1%. A polling company recently took a survey of 1000 people between the ages of 16 and 24 and found 6.5% of them are high school dropouts. The polling company would like to determine whether the dropout rate has decreased. At a 5% significance level, the p-value is
p = 0.0319
A school teacher is worried that the concentration of dangerous, cancer-causing radon gas in her classroom is greater than the safe level of 4pCi/L. The school samples the air for 36 days and finds an average concentration of 4.4pCi/L with a standard deviation of 1pCi/L. At a 5% significance level, the decision is to
reject H0, we can conclude that the mean concentration of radon gas is greater than the safe level
The owner of a large car dealership believes that the financial crisis decreased the number of customers visiting her dealership. The dealership has historically had 800 customers per day. The owner takes a sample of 100 days and finds the average number of customers visiting the dealership per day was 750. Assume that the population standard deviation is 350. At the 5% significance level, the decision is to
reject H0, we can conclude that the mean number of customers visiting the dealership is significantly less than 800
A university interested in tracking its honors program believes that the proportion of graduates with a GPA of 3.00 or below is less than 0.20. In a sample of 200 graduates, 30 students have a GPA of 3.00 or below. At a 5% significance level, the decision is to
reject h0, we can conclude that the proportion of graduates with a GPA of 3.00 or below is significantly less than 0.20
If all possible samples of size n are drawn from a population, the probability distribution of the sample mean is called the
sampling distribution
A car dealer who sells only late-model luxury cars recently hired a new salesman and believes that this salesman is selling at lower markups. He knows that the long-run average markup in his lot is $5,600. He takes a random sample of 16 of the new salesman's sales and finds an average markup of $5,000 and a standard deviation of $800. Assume the markups are normally distributed. What is the value of an appropriate test statistic for the car dealer to use to test his claim?
t = -3.00
A school teacher is worried that the concentration of dangerous, cancer-causing radon gas in her classroom is greater than the safe level of 4pCi/L. The school samples the air for 36 days and finds an average concentration of 4.4pCi/L with a standard deviation of 1pCi/L.
t = 2.40 5% significant: positive 1.690
Private universities claim to offer a higher quality education compared to public universities as justification for their more expensive tuition rates. The implication is that better education in the classroom leads to better employees after graduation. As a HR specialist in charge of selecting the best possible future employees from a pool of applicants, you propose giving preference to applicants with degrees from private universities. Hoping to control for the influence of academic performance on on-the-job performance, you randomly select 25 pairs of employees based on their cumulative GPA, one with a degree from a private university and another with a degree from a public university, and record their last performance evaluation score in an Excel file. The data appears as follows:
t test: Paired two sample for means Performance evaluation score H0: µD = 0, H1: µD > 0 Non-experimental study
A fast-food franchise is considering building a restaurant at a busy intersection. A financial advisor determines that the site is acceptable only if, on average, more than 300 automobiles pass the location per hour. The advisor tests the following hypotheses: Ho: u < 300 Ha : u > 300 The consequences of committing a Type I error would be that
the franchiser builds on an unacceptable site
The owner of a large car dealership believes that the financial crisis decreased the number of customers visiting her dealership. The dealership has historically had 800 customers per day. The owner takes a sample of 100 days and finds the average number of customers visiting the dealership per day was 750. Assume that the population standard deviation is 350. The population parameter to be tested is ___________
the mean number of customers visiting the dealership per day
The Boston public school district has had difficulty maintaining on-time bus service for its students ("A Year Later, School Buses Still Late," Boston Globe, October 5, 2011). Suppose the district develops a new bus schedule to help combat chronic lateness on a particularly woeful route. Historically, the bus service on the route has been, on average, 12 minutes late. After the schedule adjustment, the first 36 runs were an average of 8 minutes late. As a result, the Boston public school district claimed that the schedule adjustment was an improvement-students were not as late. Assume a population standard deviation for bus arrival time of 12 minutes.
z= -2.00 Yes, since the p-value is less than alpha
Vermont-based Green Mountain Coffee Roasters dominates the market for single-serve coffee in the United States, with its subsidiary Keurig accounting for approximately 70% of sales ("Rivals Try to Loosen Keurig's Grip on Single-Serve Coffee Market," Chicago Tribune, February 26, 2011). But Keurig's patent on K-cups, the plastic pods used to brew the coffee, is expected to expire in 2012, allowing other companies to better compete. Suppose a potential competitor has been conducting blind taste tests on its blend and finds that 47% of consumers strongly prefer its French Roast to that of Green Mountain Coffee Roasters. After tweaking its recipe, the competitor conducts a test with 144 tasters, of which 72 prefer its blend. The competitor claims that its new blend is preferred by more than 47% of consumers to Green Mountain Coffee Roasters' French Roast. What is the value of the appropriate test statistic to test this claim?
z=0.721 No, since the value of the test statistic is less than the critical value
