Stats midterm
Which of the following is not true about standard deviation?
If the units for the data are in inches, standard deviation is in square inches.
Shown below are box plots describing the distribution of prices paid for homes in two suburbs of Columbus, Ohio over a single 30-day period in 2016. Which of the following statements is supported by the information in this graph?
The median house price in Dublin is higher than the 75th percentile of house price in Westerville.
A percentile is a measure of
spread
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.
Which of the following statements are true? I. The area under a Normal curve is always 1, regardless of the mean and standard deviation. II. The mean is always equal to the median for any Normal distribution. III. The interquartile range for any Normal curve extends from one standard deviation below the mean to one standard deviation above the mean.
I and II
Event A has probability 0.4. Event B has probability 0.5. If A and B are independent, what is the probability that both events occur?
0.2
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
The density curve below shows the distribution of a variable that takes values from 0 to 1. What percent of the observations lie between 0 and 0.5?
25%
A scatterplot is used to
show the relationship between the height of female students and the heights of their mothers.
The ages of people in a college class are as follows: What is true about the median age?
It must be 20
If the values in a data set are in feet, then what are the units for the standardized values?
Standardized values do not have units.
Event A occurs with probability 0.3, and event B occurs with probability 0.4. If A and B are independent, we may conclude that
all of the above
DeAnna's school bus arrives at her stop at 6:00 am. If she misses the bus, her father drives her to school. Let event B = DeAnna catches the bus and F = DeAnna makes it to her first period class on time. The tree diagram summarizes the probabilities in this situation. Given that DeAnna makes it to her first class on time, what is the probability her father drove her to school?
0.168
Event A occurs with probability 0.8. The conditional probability that event B occurs, given that A occurs, is 0.5. What is the probability that both A and B?
0.4
For the density curve shown, which statement is true?
The density curve is symmetric
Below is a two-way table summarizing the number of cylinders in selected car models manufactured in six different countries. Which of the following is a marginal distribution?
The percentage of all cars manufactured in each country.
The letters p, q, r, and s represent probabilities for the four distinct regions in the Venn diagram below. For each question, indicate which expression describes the probability of the event indicated
r/q+r
The standard deviation of 16 peoples' weights (in pounds) is computed to be 5.4. What is the variance of these measurements?
29.16
You want to take an SRS of 50 of the 816 students who live in a dormitory on campus. You label the students 001 to 816 in alphabetical order. In the table of random digits you read the entries 95592 94007 69769 33547 72450 16632 81194 14873 The first three students in your sample have labels
400, 769, and 335.
If P (A) = 0.6; P(B) = 0.2 and P(AB) = 0.10, which of the following must be true?
A and B are neither independent nor mutually exclusive
To test the effect of music on productivity, a group of assembly line workers are given portable mp3 players to play whatever music they choose while working for one month. For another month, they work without music. The order of the two treatments for each worker is determined randomly. This is
a matched pairs experiment.
In comparative trials in medicine, the placebo effect and subconscious bias on the part of the physicians evaluating treatment outcomes can be avoided by using
the double-blind technique.
Suppose a data set consists of 25 positive integers. If every value in the data set is multiplied by negative 2, which of the following values would be negative?
the mean
Researchers wish to determine if a new experimental medication will reduce the symptoms of allergy sufferers without the side effect of drowsiness. To investigate this question, the researchers randomly assigned 100 adult volunteers who suffer from allergies to two groups. They gave the new medication to the subjects in one group and an existing medication to the subjects in the other group. Forty-four percent of those in the treatment group and 28% of those in the control group reported a significant reduction in their allergy symptoms without any drowsiness. The experimental units are the
100 adult volunteers
The manager of a water park collects data on the daily high temperature and the number of customers entering the park for 15 summer weekdays. Based on these data he produces a least squares regression equation to predict y= the number of customers based on x = daily high temperature. The equation is. On one day, the high temperature was 93F and 1700 customers entered the park. Which of the following is the residual for this observation?
48.4
The mean age (at inauguration) of all U.S. Presidents is approximately Normally distributed with a mean of 54.6. Barack Obama was 47 when he was inaugurated, which is the 11th percentile of the distribution. Which of the following is closest to the standard deviation of presidents' ages?
6.18
A review of voter registration records in a small town yielded the following table of the number of males and females registered as Democrat, Republican, or some other affiliation. Which of the following conclusions seems to be supported by the data?
here appears to be an association between gender and political party registration.
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 parents' income, and you expect to see a positive association
You are told that your score on an exam is at the 85th percentile of the distribution of scores. Which of the following is a correct interpretation of this information?
your score was higher than approximately 85% of the people who took this exam.
A candidate for mayor of Dallas wants to know what proportion of city residents support his candidacy. His staff calls 1,000 people chosen at random from the city telephone directory and 850 of them respond. What are the population and the sample in this example?
Population: all Dallas residents. Sample: the 850 people who respond
The mean height of men in the United States is 69 inches and the standard deviation is 3 inches. For U.S. women, the mean is 64 inches and the standard deviation is 2.7 inches. The tallest women in the Women's National Basketball Association is Brittney Griner, who is 80 inches tall (6 feet 8 inches). The tallest current player in the Men's NBA is Hasheem Thabeet, who is 87 inches tall (7 feet 5 inches). Which player is taller relative to others of the same sex in the U.S.?
Thabeet, because his z- score is greater.
A sportswriter wants to know how strongly Lafayette residents support the local minor league baseball team, the Lafayette Leopards. She stands outside the stadium before a game and interviews the first 20 people who enter the stadium. The newspaper asks you to comment on their survey method. You say,
This is a convenience sample. It will almost certainly overestimate the level of support among all Lafayette residents.
Event A has probability 0.4. Event B has probability 0.5. If A and B are mutually exclusive, what is the probability that both events occur?
0
If your score on a test is at the 60th percentile, you know that your score lies
Between the median and the third quartile.
A basketball player makes 2/3 of his free throws. To simulate a single free throw, which of the following assignments of digits to making a free throw are appropriate? I. 0 and 1 correspond to making the free throw and 2 corresponds to missing the free throw. II. 01, 02, 03, 04, 05, 06, 07, and 08 correspond to making the free throw and 09, 10, 11, and 12 correspond to missing the free throw. III. Use a die and let 1, 2, 3, and 4 correspond to making a free throw while 5 and 6 correspond to missing a free throw.
I, II, and III
The following scatter plot presents data on wine consumption (in liters per person per year) and death rate from heart attacks (in deaths per 100,000 people per year) in 19 developed Western countries. Do these data provide strong evidence that drinking wine actually causes a reduction in heart disease deaths?
No. Countries that drink lots of wine may differ in other ways from countries that drink little wine. We can't be sure the wine accounts for the difference in heart disease deaths
The bar graph at right shows the distribution of religious affiliation around the world. Which of the following statement best describes what is wrong with this graph?
Starting the vertical scale at 5 distorts the relative frequency of the religions.
Which of the following are most likely to be negatively correlated?
The prices and the weights of all racing bicycles sold last year in Chicago
Consider the following scatterplot of amounts of CO (carbon monoxide) and NOX (nitrogen oxide) in grams per mile driven in the exhausts of cars. The least-squares regression line has been drawn in the plot In the scatterplot, the point indicated by the open circle
as a negative value for the residual.
Two variables are said to be negatively associated if
larger values of one variable are associated with smaller values of the other.
The fraction of the variability in the values of a response y that is explained by the least-squares regression with x= the explanatory variable is the
square of the correlation coefficient.
The correlation coefficient measures
the strength of the linear relationship between two quantitative variables.
Here is an assignment of probabilities to the face that comes up when rolling an unusual die once Which of the following is true?
this is a legitimate assignment of probability.
Mrs. Austin measures the age, marital status, and earned income of an SRS of 1463 women. The number and type of variables you have measured is
three; one categorical and two quantitative
An efficiency consultant determines that on the assembly line at Widget Manufacturing, 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. He finds that 70% of the variability in widgets produced per hour can be explained by the least-squares regression line. Which of the following is the best approximation of the correlation of x and y?
-0.84
The area under the standard Normal curve corresponding to -0.5 <z< 1.2 is closest to what value?
.5764
Which of the following statements about a randomized block design with two treatments is true?
All the units in Block A share the same (or similar) values of the blocked variable.
The most important advantage of experiments over observational studies is that
experiments can give better evidence of causation.
The customer service department of an online store keeps track of the length of time customers wait on hold for a representative. The mean wait time is 5 minutes and the standard deviation is 2.3 minutes. Suppose the company wants to change the variable from minutes to seconds exceeding a target time of 120 seconds. That is, if X is wait time in minutes, the new variable is Y = 60X- 120. Which of the following are the mean and standard deviation of Y?
mean = 180, standard deviation = 138
Below is the computer output for a least-squares regression of y= protein (in grams) and x= calories for 16 different sandwiches produced by a major sandwich franchise. Which of the following best describes what S= 5.723 represents?
When using this regression to predict protein content from calories content, we will typically be off by about 5.723 grams.
A least-squares regression line for predicting weights of basketball players based upon their heights produced the residual plot below. What does the residual plot tell you about the linear model?
the curved pattern in the residual plot suggests that the linear model is not appropriate.
Data was recorded on wine consumption (in liters per person per year) and death rate from heart attacks (in deaths per 100,000 people per year) in 19 developed Western countries and a scatterplot was constructed. The wine consumption data are in liters of alcohol per person. Which of these are all measured in liters of alcohol per person?
the mean, the median, and the standard deviation of wine consumption
The least-squares regression line is fit to a set of data. If one of the data points has a positive residual, then
the point must lie above the least-squares regression line.
If 30 is added to every number on a list, which one of following does not change?
the standard deviation
Here are the exam scores for the 15 students in Mr. Kirk's statistics class: 72 75 75 78 81 81 85 89 90 90 90 91 95 95 98. Karen was at the 20th percentile of the distribution. What score did Karen earn on the exam?
78
A fisheries biologist studying whitefish in a Canadian Lake collected data on the length (in centimeters) and egg production for 25 female fish. A scatter plot of her results and computer regression analysis of egg production versus fish length are given below. Note that number of eggs is given in thousands (i.e., "40" means 40,000 eggs). What is the equation of the least-squares regression line?
Eggs = -142.74 + 39.25 (Length)
Which of the following statements are true about the least-squares regression line? I. The slope is the predicted change in the response variable associated with a unit increase in the explanatory variable. II. The line always passes through the point the means of the explanatory and response variables. III. It is the line that minimizes the sum of the squared residuals.
I, II, and III are all true.
A study gathers data on the outside temperature during the winter, in degrees Fahrenheit, and the amount of natural gas a household consumes, in cubic feet per day. Call the temperature x and gas consumption y. The house is heated with gas, so x helps explain y. The least-squares regression line for predicting y from x is When the temperature goes up 1 degree, what happens to the gas usage predicted by the regression line?
It goes down 19 cubic feet.
Control groups are used in experiments in order to accomplish which one of the following?
Limit the effects of variables other than the explanatory variable on the outcome
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 similar as possible
A television station is interested in predicting whether voters in its viewing area are in favor of offshore drilling. It asks its viewers to phone in and indicate whether they support/are in favor of or are opposed to this practice. Of the 2241 viewers who phoned in, 1574 (70%) were opposed to offshore drilling. The viewers who phoned can best be described as
a voluntary response sample.
The following is a histogram showing the actual frequency of the closing prices of a particular stock on the New York Stock Exchange over a 50-day period. Without doing any calculations compare the values of the mean and the median.
the mean is larger than the median because the histogram is skewed to the right.
A policeman records the speeds of cars on a certain section of roadway with a radar gun. The histogram below shows the distribution of speeds for 251 cars. The maximum value is 35 mph. If the value, 35 mph, was actually 29 mph, how would the mean and standard deviation change?
the mean would stay nearly the same and the standard deviation would decrease
You can roughly locate the mean of a density curve by eye because it is
the point at which the curve would balance if made of solid material.
A stratified random sample is appropriate when
the population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between groups.
If I toss a fair coin 5000 times
the proportion of heads will be close to 0.5.
The probability of any outcome of a random phenomenon is
the proportion of times the outcome occurs in a very long series of repetitions.
A farmer wishes to determine which of two brands of baby pig pellets, Kent or Moormans, produces better weight gains. Two of his sows each give birth to litters of 10 pigs on the same day, so he decides to give the baby pigs in litter A only Kent pellets, while the pigs in litter B will get only Moormans pellets. After four weeks, the average weight gain for pigs in litter A is greater than the average weight gain for pigs in litter B. The weight of the pigs after four weeks is
the response variable
A marketing research firm wishes to determine if the adult men in Laramie, Wyoming, would be interested in a new upscale men's clothing store. From a list of all residential addresses in Laramie, the firm selects a simple random sample of 100 homes and mails a brief questionnaire to each. The chance that all 100 homes in a particular neighborhood in Laramie end up being the sample of residential addresses selected is
the same as for any other set of 100 residential addresses.
Just before the presidential election of 1936, the magazine Literary Digest predicted—incorrectly, as it turned out—that Alf Landon would defeat Franklin Delano Roosevelt. Landon lost in a landslide. It turned out that the magazine had only polled its own subscribers, plus others from a list of automobile owners and a list of people who had telephone service. All three groups had higher than typical incomes during the Great Depression. This is an example of
uncoverage
Suppose that A and B are independent events with P(A) = 0.2 and P(B) = 0.4.and. P(A BC) =
0.12
The five-number summary for scores on a statistics exam is 11, 35, 61, 70, 79. In all, 380 students took the test. About how many students had scores between 35 and 61?
95
For the density curve shown, which of the following is true?
All of the above are true.
The distribution of the heights of students in a large class is roughly Normal. Moreover, the average height is 68 inches, and approximately 95% of the heights are between 62 and 74 inches. What is the standard deviation of the height distribution?
B
A sample of student opinion at a Big Ten university selects an SRS of 200 of the 30,000 undergraduate students and a separate SRS of 100 of the 5,000 graduate students. What is the term for this kind of sample?
Cluster sample
Mr. Swartzentruber selects a random sample of 100 students in grades 10 through 12 and asks their year in school and whether they were involved in interscholastic sports, intramural sports, or no sports. The results are summarized in the segmented bar graph below. Based on this graph, which of the following statements is true?
Juniors have the highest percentage participation in intramurals
To assess the effects of exercise on reducing cholesterol, a researcher took a random sample of fifty people from a local gym who exercised regularly and another random sample of fifty people from the surrounding community who did not exercise regularly. They all reported to a clinic to have their cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of whether subjects exercised regularly. This is a(n
double blind experiment.
Which of the following best describes the correlation r?
he average of the products of the standardized scores of x and y for each point.
The mean finish time for 48 racers who finished the grueling 50km cross-country ski race at the 2010 Vancouver Olympics is 2.164 hours and the standard deviation is 0.85 hours. The distribution is skewed to the right. What are the mean, standard deviation, and shape of the distribution of z-scores of the same data?
mean = 0, standard deviation = 1, skewed to the right
A local tax reform group polls the residents of the school district and asks the question, "Do you think the school board should stop spending taxpayers' money on non-essential arts programs in elementary schools?" The results of this poll are likely to
underestimate support for arts programs because of the way the question is worded.
Jessica was studying starfish populations and collected starfish of the species Pisaster . She was interested in the distribution of sizes of starfish on a certain shoreline. One measure of size is "arm length." Below is a cumulative relative frequency distribution for the arm length, in centimeters, of 102 Pisaster individuals. The Pisaster arm length of a particular starfish is 18.20 cm. Is this starfish unusually large?
yes, this star fish is approximately at the 90th percentile for Pisaster arm length.
A basketball player shoots 8 free throws during a game. The sample space for counting the number she makes is
{0, 1, 2, 3, 4, 5, 6, 7, 8}.
A jar contains 60 red marbles and 40 white marbles. Mrs. Dentato draws 15 marbles randomly from the jar without replacement. The dotplot below shows the number of red marbles (out of 15) drawn in 200 computer simulations of this random process. Based on this dotplot, which of the following is the best estimate of the probability of drawing 3 or fewer white marbles (out of 15) from the jar?
0.035
The probability of a randomly selected adult having a rare disease for which a diagnostic test has been developed is 0.001. The diagnostic test is not perfect. The probability the test will be positive (indicating that the person has the disease) is 0.99 for a person with the disease and 0.02 for a person without the disease. If a randomly selected person is tested and the result is positive, what is the probability the individual has the disease?
0.047
If you buy one ticket in the Provincial Lottery, then the probability that you will win a prize is 0.11. Given the nature of lotteries, the probability of winning is independent from month to month. If you buy one ticket each month for five months, what is the probability that you will win at least one prize?
0.44
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, of course!). What is the probability that the two socks match?
0.500
Mrs. Levy asked 100 high school students if they had a dog, a cat, or both at home. Here are the results. If two students are selected at random, with replacement, what is the probability that neither of them has a dog or a cat?
0.548
Experience has shown that a certain lie detector will show a positive reading (indicates a lie) 10% of the time when a person is telling the truth and 95% of the time when a person is lying. Suppose that a random sample of 5 suspects is subjected to a lie detector test regarding a recent one-person crime. What is the probability of observing no positive readings if all suspects plead innocent and are telling the truth?
0.590
Mrs. Young asked 100 high school students if they had a dog, a cat, or both at home. Here are the results If a single student is selected at random and you know she has a dog, what is the probability she also has a cat?
0.75
Mrs. Auld asked 100 high school students if they had a dog, a cat, or both at home. Here are the results. If a single student is selected at random, what is the probability associated with the union of the events "has a dog" and "does not have a cat?"
0.9
Consider the following scatterplot of the amount of CO (carbon monoxide) and NOX (nitrogen oxide) in grams per mile driven in the exhausts of cars. The least-squares regression line has been drawn in the plot. Based on the scatterplot, the least-squares regression line would predict that a car that emits 10 grams of CO per mile driven would emit approximately how many grams of NOX per mile driven?
1.1
In a certain town, 60% of the households have fiber optic internet access, 30% have at least one high-definition television, and 20% have both. What percent of households have neither fiber optic internet or high-definition television?
30%
Suppose we roll two six-sided dice, one red and one green. Let A be the event that the number of spots showing on the red die is three or less and B be the event that the number of spots showing on the green die is three or more. P(AB)
5/6
The risk of an investment is measured by the variability of the changes in its value over a fixed period, such as a year. More variation from year to year means more risk. The government's Securities and Exchange Commission wants to require mutual funds to tell investors how risky they are. A New York Times article says that some people think that "the proposed risk descriptions, especially one that goes by the daunting name standard deviation" are hard to understand. Explain to a friend what the standard deviation means, using the fact that the changes in a mutual fund's value over many years have a roughly Normal distribution.
Start with the average (mean) change in the fund's value over many years; the actual change will be within one standard deviation of that average in about 68% of all years.
Mrs. Richardson asked the 26 seniors in her statistics class how many AP® courses they had taken during high school. Below is a dotplot summarizing the results of her survey. Which of the following is a correct boxplot for these data?
b
The tables below shows the results of the New Hampshire Republican Primary on January 10, 2012. Which of the following lists of graphs are all appropriate ways of presenting these data?
bar graph, pie chart
The statistics given below provide a summary of the distribution of IQ scores of a random sample of 280 elementary school children. Approximately 210 children have IQs that are
between 95 and 122
An airline that wants to assess 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
cluster sample
Suppose a straight line is fit to data having response variable y and explanatory variable x. Predicting values of y for values of x outside the range of the observed data is called
extrapolation
An experiment was conducted by some students to explore the nature of the relationship between a person's heart rate (measured in beats per minute) and the frequency at which that person stepped up and down on steps of various heights. Three rates of stepping and two different step heights were used. A subject performed the activity (stepping at one of the three stepping rates at one of the two possible heights) for three minutes. Heart rate was then measured at the end of this period. The variables "stepping rate" and "step height" are the
factors
Suppose we roll two six-sided dice, one red and one green. Let A be the event that the number of spots showing on the red die is three or less and B be the event that the number of spots showing on the green die is three or more. The events A and B are
independent.
A new headache remedy was given to a group of 25 subjects who had headaches. Four hours after taking the new remedy, 20 of the subjects reported that their headaches had disappeared. From this information you conclude
nothing, because there is no control group for comparison
A study was conducted to quantify the relationship between stopping distance (in feet) and air temperature (in degrees Celsius) for a certain 2,000-pound car travelling 40 mph. If the stopping distance were measured in meters rather than feet (1 meter = approx. 3.28 feet), how would the correlation r change?
r would not change, because the calculation of r does not depend on the units used.
The Bradley effect is a theory proposed to explain observed discrepancies between voter opinion polls and election outcomes in some elections where a white candidate and a non-white candidate run against each other. The theory proposes that some voters tend to tell pollsters that they are undecided or likely to vote for a non-white candidate, and yet, on election day, vote for the white opponent. This is an example of
response bias
In an experiment, an observed effect so large that it would rarely occur by chance is called
statistically significant.
The scatterplot below displays the relationship between carbohydrate content (in grams) and protein content (in grams) for 17 different 6" sandwiches at Subway. The two points on the far right (indicated with open circles) represent the Meatball Marinara sandwich and the Applewood Pulled Pork sandwich. If these two points were removed from the data, how would the correlation and the slope of the least-squares regression line change?
the correlation would increase and the slope of the regression line would increase
There are 10 students in Mrs. Meizius's afternoon Statistics class. The maximum point total for the most recent quarter was 200 points. The point totals for the 10 students are given in the stemplot below. Based upon the shape of the stemplot, we can conclude that
the mean is greater than the median.
The cumulative relative frequency graph below shows the distribution of lengths (in centimeters) of fingerlings at a fish hatchery. The interquartile range for this distribution is approximately
1.2 centimeters.
Consider the following scatterplot of amounts of CO (carbon monoxide) and NOX (nitrogen oxide) in grams per mile driven in the exhausts of cars. The least-squares regression line has been drawn in the plot. What is the approximate value of the intercept of the least-squares regression line?
1.8
A lobster fisherman is keeping track of the productivity of a set of traps he has placed in a favorite location. Below are the numbers of lobsters in these traps over the course of 12 different hauls. According to the outlier rule, which values are outliers?
14 only
A company produces packets of soap powder that are labeled "Giant Size 32 Ounces." The actual weight of soap powder in a box has a Normal distribution with a mean of 33 oz. and a standard deviation of 0.7 ounces. 95% of packets actually contain more than x ounces of soap powder. What is x?
31.85
Mr. Stephens has a colony of bongo spiders in his classroom. There are 1000 adult spiders in the colony, and their weights are Normally distributed with mean 11 grams and standard deviation 2 grams. About how many spiders are there in the colony which weigh more than 12 grams?
310
A researcher wishes to study how the average weight y (in kilograms) of children changes during the first year of life. He plots these averages versus the age x (in months) and decides to fit a least-squares regression line to the data with x as the explanatory variable and y as the response variable. He computes the following quantities. r= correlation between x and y = 0.9 x-bar= mean of the values of x= 6.5 y-bar= mean of the values of y = 6.6 sx = standard deviation of the values of x = 3.6 sy = standard deviation of the values of y = 1.2 What is the y-intercept of the least-squares regression line?
4.65
Deciduous forests in the eastern united states often have many different species of oak trees. Below is a frequency distribution for five different species of oaks found in sample plots of a certain forest. Which of the following pie charts describes the same distribution?
C
Which of these variables is least likely to have a Normal distribution?
annual income for all 150 employees at a local high school
The mean age of four people in a room is 30 years. A new person whose age is 55 years enters the room. What is the mean age of the five people now in the room?
35
A farmer wishes to determine which of two brands of baby pig pellets, Kent or Moormans, produces better weight gains. Two of his sows each give birth to litters of 10 pigs on the same day, so he decides to give the baby pigs in litter A only Kent pellets, while the pigs in litter B will get only Moormans pellets. After four weeks, the average weight gain for pigs in litter A is greater than the average weight gain for pigs in litter B. The feed they get is not the only factor affecting the rate at which pigs gain weight. Genetic differences also affect weight gain. It is likely that the pigs in litter A are genetically different from the pigs in litter B, because the two litters have different mothers. Because the farmer is only interested in determining which brand of pellets is better, the study suffers from
confounding
All but one of the following statements contains an error. Which statement could be correct?
he correlation between mid-August soil moisture and the per-acre yield of tomatoes is r= 0.53.
Which of the following statements about standard deviation is true?
standard deviation is always a non-negative number.
Suppose that 16-ounce bags of chocolate chip cookies are produced with weights that follow a Normal distribution with mean weight 16.1 ounces and standard deviation 0.1 ounce. Approximately what percent of the bags will likely be underweight (that is, less than 16 ounces)?
16%
The following table compares the hand dominance of 200 Canadian high-school students and what methods they prefer using to communicate with their friends. Suppose one student is chosen randomly from this group of 200. Which of the following statements supports the conclusion that the event "Right-handed" and the event "Online" are not independent?
51/60166/20
The histogram below shows the distribution of heights for 100 randomly selected school children in Great Britain. Which of the following descriptions best fits this distribution?
Roughly symmetric, centered at about 150, range: 80
A farmer wishes to determine which of two brands of baby pig pellets, Kent or Moormans, produces better weight gains. Two of his sows each give birth to litters of 10 pigs on the same day, so he decides to give the baby pigs in litter A only Kent pellets, while the pigs in litter B will get only Moormans pellets. After four weeks, the average weight gain for pigs in litter A is greater than the average weight gain for pigs in litter B. The feed they get is not the only factor affecting the rate at which pigs gain weight. Genetic differences also affect weight gain. It is likely that the pigs in litter A are genetically different from the pigs in litter B, because the two litters have different mothers. Because the farmer is only interested in determining which brand of pellets is better, the study suffers from
onfounding
Below is a histogram of the heights of gold-medal-winning high jumps in the Olympic Games since 1896. Which of the following statements is supported by this histogram?
The median jump is between 80 and 85 inches.
One way economists measure the health of real estate market is by counting "housing stats," or the number of permits issued for construction of new homes. Below is a graph displaying housing stats (in thousands) in the United States from 2006 to 2009. What is the principle weakness of this graphical presentation of data?
Using proportionally-sized pictograms exaggerates the difference between years.
A stats teacher asks the 29 students in his stats class how many minutes they spent on one homework assignment. The distribution of the variable "time on homework" is
a description of what values the variables takes and how often it takes them.