stats midterm
the probability is approximately 0.6 that, in a randomly selected week, dan will make less than
$255
a efficiency consutant determines that on the assembly line at widget maufacturing, there is a strong, negative, linear relationship between x= the number of consecutive hours a worker has been assembling widgets and y= the number of widgets he can produce in an hour. which of the following is the best approximation of the correlatin of x and y?
-0.84
use scenario 5-1 you select one musician from this group at random. what is the probability that this person plays a woodwind?
0.159
You select one musician from this group at random. What is the probability that this person plays a woodwind?
0.182
jun and deron are applying for summer jobs at a local restaurant. after interviewing them, the restraunt owner says "the probability that i hire jun is 0.7 and the probabilty that i hire deron is .4 the probability that i hire at least one of you is 0.9 what is the probability that both jun and deron gets hired?
0.2
what is p(x>$400)
0.2199
what is the probability that a randomly chosen house hold has at least two televisions?
0.39
in your top dresser drawer are 6 blue socks and 10 grey socks, unpaired and mixed up. one dark morning you pull two socks from the drawer (without replacement) what is the probability that the two socks match?
0.500
if he is at the bus stop for three consecutive days at 7:30 am what is the approximate probability that he catches the bus all three days?
0.614
the probability that a certain crate has more than 4 contaminated chickes is
0.8889
here are the IQ tests scores of 10 randomly chosen fifth grade students:
09, 10, 11, 12, 13, 14
a copy machine dealer has data on the number of copy machines x at each of 89 customer locations and the number of service calls in a month y at each location. summary calculations give x = 8.4, sx=2.1, sy = 3.8 and r = .86/ what is the slope of the least squares regression line of number of service calls on number of copiers?
1.56
the probability that you will be ticketed for illegal parking on campus is about 1/3. during the last nine days, you have illegally parked every day and have not been ticketed. today on the 10th day, you again decide to park illegally. assuming the outcomes are independent from day to day, the probability that you will be caught is
1/3
a restraunt maitre d wants to be able to predict the time customers will have to wait for a table
15-[2.8+3.77(4)]
in a random sample of 100 cars parked in long term parking at philidelphia internation airport, 19% of cars were white.
23% is parameter and 19% is a statistic
which one of the following could be the 60th percentile of this distribution?
4
forty pound bags of bird seed do not have exactly 40 pounds of seed, but the weight of seeds is approximately normally distributed with a mean of 40 pounds and a standard deviation of .25 pounds. which of the following is the best estimate of the 90th percentile for the weight of these bags of seed?
40.3 pounds
one characteristic of roller coasters that contributes to the maximum speed of the ride is the track;s maximum height. below are computer output and residual plot for a regression of maximum speed (in miles/hour) on maximum height (in feet) for nine roller coasters that opened recently around the world. the circled point represents a roller coaster in the philipines whose maximum height is 70 ft. the observed speed of this roller coaster is closest to
55 m/h
in the setting of question #7, about what percent of the variation in the number of service calls is explained by the linear relation between number of service calls and number of machines?
74%
a medical researcher collects health data on many women in each of several countries. one of the variable measured for each woman in the study is her weight in pounds. the following list gives the five number summary for the weights of adult women in one of the countries. about what percent of country A women weigh between 110 and 240 lbs?
75%
1200 tomatoes have a mean weight of 143 grams and a standard deviation of 35 grams. if the weights are normally distributed, approximately how many tomatoes weigh between 73 grams and 178 grams?
978
which of the following represents the probability that the mean weight of a random sample of 3 olives from this population is greater than 8 gm?
A 8-7.7/0.2/square root 3
which statement below best describes what you know about the sampling distribution of ^p?
A. the distribution is not approximately normal
Rainwater was collected in water collectors at 30 different sites near na industrials complex and the amount of acidity *pH level) was measured. The data ranged from pH 2.6 to pH 6.3. Which of the following box plots is a correct representation of the same distribution?
B
dwayne has collected data on the number of occupants of cars travelling on the road past his house for the past week. based on his data he has constructed a probability model for the number of occupants of a randomly selected car on his street.. which of the following could be his model?
B
venn diagram summarizing internet source of news and print source of news
D
which of the following expressions represents the probability that more than half the households sampled will own a DVD recorder?
E
which of the following is a true statement? I. correlation requires that there are clearly identified explanatory and response variables II. scatterplots require that both variables be quantitative III. every least squares regression line passes through
II and III only
which of the following distributions has a mean that varies from sample to sample? I the population distribution II the distribution of sample data III the sampling distribution
II only
to calculate the stdev of the sampling distribution of the sample proportion, which of the following conditions must be met?
III only
if p(A)=0.6p(B)=0.2 and p(a and b)=0.10 which of the following must be true
a and b are neither independent nor mutually exclusive
you work for an advertising agency that is preparing a new television commercial to appeal to women. you have been asked to design an experiment to compare the effectiveness of three versions of the commercial. Each subject will be shown one of the three versions and then asked her attitude towards the project. you think there may be large differences between women who are employeed outside the home and those who are not. because of these differences, when assigning groups in a specific treatment, you should use
a block design
a nutritionist wants to study the effect of storage time (6,12, and 18 months) on the amount of vitamin c present in freeze dried fruit when stored for these lengths of time. six fruit packs were randomly assigned to each of the three storage times. the treatment, experimental unit, and response are respectively:
a specific storage time, a fruit pack, amount of vitamin c
the Hemlock Woolly Adelgid is an insect that has accidentally been released in eastern US forests from asia. since it has not natural enemies in the US, it is spreading rapidly. a forester studying the abundance of the insect in southern vermont wants to determine if it has spread that far north. he randomly selects 200 hemlock trees in a large vermont forsest and finds that 46 of them show signs of damage from this insect. to which of the following groups of trees would it be appropriate to generalize the results of this study?
all hemlock trees in the forest from which the 200 trees were selected
which of the following is the best description of a simple random sample of size n from a population of size n
any method of sampling in which every group of individuals of size n is equally likely to be selected
the stdev of the sampling distribution of mean heights for the indiana sample is
approximately the same as for the purdue sample because both are samples of siize 500
forester who wants to evaluate the health of maple trees in a large forest
cluster sample
a study examined the relationship between the sepal length and sepal width for two varieties of an exotic tropical plant. varieties X and O are represented by x's and o's, respectively, in the following scatterplot. Which of the following statements is true?
considering each variety seperately, there is a negative correlation between sepal length and sepal width
an airline that wants to asses customer satisfaction chooses a random sample of 10 of its flights during a single month and asks all of the passengers on those flights to fill out a survey. this is an example of a
convenience sample
We wish to draw a sample of 5 without replacement from a population of 50 households. Suppose the households are number 01, 02,...50, and suppose that the relevant line of the random number table 11362 35692 90842 46843
households 11 36 23 08 42
if you flip three coins the probability of getting three heads is 0.125 which of the following statements follows from this?
if you flip three coins 5000 times, the percentage of time you get three heads will be very close to 12.5%
what is the principle purpose of control in a randomized comparative experiment?
isolating the effect of the treatment variable by keeping all other variables the same in the treatment groups
The mean speed of vehicles in the "cars only" lanes of the New Jersey turnpike is 68 miles per hour. The mean speed of vehicles in the "any vehicle" lanes if 64 miles per hour. What must be true about the mean sped of all vehicles on the turnpike assuming there are the only types of lanes?
it could be any number between 64 and 68 miles per hour
a materials engineer wishes to compare the durability of two different types of paving material. she has 40 different one mile stretcges of interstate highway that she's been authorized to repave for this study, she decides to carry out a matched pairs experiment. which of the following is the best way for her to carry out the randomization for this study?
let each of the 40 roadways act as its own pair, dividing each roadway into the first half mile and the second half mile. flip a coin for each of the 40 roadways to decide which half mile gets which pavement
the mean and stdev of the number of contaminated chickens in a crate are
m=7.2, s=2.24
a track coach wants to test the effectiveness of a new training program for distance runners. he selects his two fastest runners and, using a coin flip, randomly chooses one to participate in the new program. the other will continue with the standard training regimen. he then picks the next two fastest runners and randomly addigns one to each program, he repeats this process with all his runners, choosing the two fastest remaining each time. he then compares race times within each group of two runners. what is the name for this kind of experimental design?
matched pairs design
which of the following are the mean & approximate stdev of the total weight of lobsters john traps in a day?
mean 22, stdev 8.32
a biology teacher has just finished grading a quiz for a class of 26 students and has calculated measure of center and spread on the scores. while writing the grades on the quizzes, he realizes he made a mistake, and the highest grade should be 10 points higher. which one of the following sets of measurements will he have to recalculate?
mean and stdev
you are interested in predicting the cost of heating houses on the basis of how many rooms the house has. a scatterplot of 25 houses reveals a strong linear relationship between these variables, so you calculate a least squares regression line. least squares refers to
minimizing the sum of the squares of the residuals
there are 1200 students at highland highschool
no, bc the sample is more than 10% of the population
identify the types of bias involved in the following study: a political pollster seeks information about the proportion of american adults who oppose gun controls. he asks and SRS of 1000 american adults: "do you agree or disagree with the following statement: americans should preserve their constitutional right to keep and bear arms" a total of 910 or 91% said agree
question wording bias (nonsampling error)
which of the following best describes the distribution the variable number of words in these essays?
skewed right, centered about 750, with one high outlier
an airline has 10 daily flights from philadelphia to denver. to asses customer satisfaction, a random sample of 15 passengers from each flight on a single day are asked to fill out a survey about their experience on the flight. what type of sample is this?
stratified random sample
some studies of the relationship between car color and frequency of accidents have found that red cars are more likely to be in accidents than black cars, despite how visible they are. some experts warn that we should not conclude that red cars are less safe than black cars, becuase of possible confounding. which of the following best describes what this means?
studies of this type are all observational, and it is not possible to seperate the effect of the car color from the type of people who choose to drive red cars
the scatterplot at right shows the relationship between carbohydrates and protein in one-cup serving of 15 different varieties of beans. the unusual point in the upper left part of the plot for navy beans, with 15.8 grams of protein and 15.8 grams of carbohydrates. which of the following best describes how correlation would change if we removed navy beans from the data set?
the correlation would be closer to 1, because the remaining data would have a stronger positive relationship
the mean birth weight of infants born at a certain hospital in the month of april was 128 oz with a standard deviation of 10.2 oz. which of the following is a correct interpretation of standard deviation?
the distance between the weight of each infant born in april and the mean weight was on average about 10.2 oz
vermont is particularly beautiful in early october during foliage season
the distribution of sample proportions from all possible samples of size 50 from the population of cars passing the exit on I-91
there is an appoximate linear relationship between the height of females and their age (from 5 to 18 years) described by the equation height=50.3 + 6.1(age), where height is measured in centimeters and age in years. which of the following statements must be true?
the estimated slope is 6.1, which implies that female children between the ages of 5 and 18 increase in height by about 6.1 cm for each year they grow older
which of the following is true about the events "plays a woodwine" and "male"
the events are not mutually exclusive nor are they independent
you have data for many families on the parents income and the years of education their eldest child completes. your initial examination of the data indicates that children from wealthier families tend to go to school for longer. when you make a scatterplot,
the explanatory variable is parent's income, and you expect to see a positive association
the central limit theorem says that
the mean burnout time for a large number of bulbs has a distribution that is close to normal
if a distribution is skewed to the right, which of the following is true?
the mean must be greater than the median
the time it takes people to finish a certain kind of puzzle is strongly skewed right. which of the following statements is true about the mean and median of this distribution?
the mean will be greater than the median
a small company that prints custom t shirts has 6 employees, one of whom is the owner and manager. suppose the owner makes $120,000 per year and the other employees make between $40,000 and $50,000 per year. One day, the owner decides to give himself a $30,000 raise. Which of the following describes how the company's mean and median salaries would change?
the mean would increase by $5000 and the median would not change
which of the following random variables is geometric?
the number of digits i will read beginning at a randomly selected starting point in a table of random digits until i find a 7
A sample of 250 high school students were asked " If you had $1000 to contribute to one kind of charitable organization, which type of organization would you choose? which of the following seems to be supported by the data
the proportion of males who said they would contribute to an environmental organization was higher than the proportion of females who said they would contribute such an organization
A study of the fuel economy for various automobiles plotted the fuel consumption (in liters of gasoline used per 100 kilometers traveled) vs. speed (in kilometers per hour). A least- squares line was fit to the data. Here is the residual plot from this least-squares fit.What does the residual plot tell you about the linear model?
the residual plot clearly indicates that the data isnt linear
forty percent of these show signs of damages, which of the following statements is correct?
the sampling distribution of the sample proportion of damaged trees is approximately normal
in the setting of question #10, which of the following best describes what s= 10.5371 represents in this setting?
the standard deviation of the residuals - observed height minus predicted height
at right is the stemplot of the weights of 18 adult main coon cats
the standard score for a 14 pound cat is negative
a recent investigation of prices for five-year-old toyota camrys in montgomery, alabama, and new york, new york revealed that the mean price in montgomery was $13,200 with a standard deviation of $1000. in new york, the mean price was $12,800 with a standard deviation of $1800. which of the following statements is true?
the standard score for a car priced at $15,000 would be higher in montgomery than in new york
suppose we want to compare the proportion of texas residents
the variances of the sampling distibutions with be nearly the same if we sample the same number of residents of each state
the pie chart at right describes the distribution of state tree types for the 50 states in the united states. the category "other" includes all trees that are the state tree for 2 or fewer states. which of the following conclusions can we draw from this chart?
there are 10 states that have designated a pine as their state tree
the following bar graph gives the percent of owners of three brands of trucks who are satisfied with their truck. from this graph, we may conclude
there are only small differences in the satisfaction of owners for the three brands
which of the following is the most important reason for randomly assigning subjects to treatment groups in an experiment?
to create groups that are as similiar as possible
which of the following best describes the mean and stdev of the standard scores of these pomegranates?
ux= 0, ox= 1
a student investigating study habits asks a simple random sample of 17 students
ux=45, ox=3.75, shape of distribution unknown
eighty volunteers who currently use a certain brand of over the counter allergy medication have been recruited to participate in a trial of a new allergy medication. the volunteers are randomly assigned to one of two groups. one group continue to take their current medication, the other group switches to the new experimental medication. each is asked after two weeks if their allergy symptoms are worse, better, or about the same as they were at the start of the study. which of the follow best describes a conclusion that can be drawn from this study?
we can determine whether the new drug reduces symptoms more than the old drug for the subjects in the study
an agriculture economist says that the correlatioin between corn prices and soybean prices is r=0.7. this meas that
when corn prices are above average, soybean prices also tend to be above average
a survey is to be administered to recent graduates of a certain nursing school in order to compare the starting salaries of women and men. for a random sample of graduates, three variables are to be recorded: sex, starting salary, and area of specialization. which of the following best describes a conclusion that can be drawn from this study?
whether there is an association between sex and starting salary among graduates of this nursing school
you select 40 cars from a regular deck of 52 cards. let y be the number of red cards in the 40 collected
y has a binomial distribution with n=40 observations and probability of success p=0.5, provided that after selecting a card it is replaced in the deck and the deck is shuffled well before the next card is selected
a randomly chosen subject arrives fr a study of excercise and fitness and begins walking on a treadmill at a brisk pace. which of the random variables described below is discrete?
you measure the maximum heart rate in beats per minute
