AP Stats Midterm Review
Ch.3 Leonardo da Vinci, the renounced painter, speculated that an ideal human would have an arm span (distance from the outstretched fingertip of the lefthand to the outstretch fingertips of the righthand ) that was equal to his height. Is it possible to predict arm span from height? The following computer regression printout shows the results of a least-squares regression of arm span on height, both in inches, for a sample of 18 high school students.
If one of the students in the sample had a height of 70 inches and an arm span of about 68 inches, then the residual for this student would be about -2.36 inches. (a.)
Ch.3 A scatterplot of the relationship between the cost of tuition at a typical four-year private college versus year (from 1976 through 2010) displayed a nonlinear relationship. A least-squares regression analysis of 1n(cost of tuition) versus year was conducted to determine if the relationship between year and cost can be described by an exponential relationship. The analysis produced the following residual plot.
No, the residual plot does not display random scatter about the line residual = 0 (c.) or possibly No, the residual plot shows us that a quadratic model is appropriate for these data. (d.)
Ch.4 (corrected) You can use voice over Internet Protocol (VoIP) to make long-distance calls over the internet. one of these most popular VoIP Services is Skype. how would the appearance of add during calls affect the use of this service? researchers design an experiment to find out. they recruit 300 people who have not use Skype before to participate some people get the current version of Skype with no ads, While others the ads and everything that called the researchers are interested in the frequency and length of the phone calls. the treatment, experimental unit, and response are respectively:
Skype with/without ads, 300 people, length and frequency of calls (c.)
Ch.4 Some medical investigations have instigations indicated that nonsmokers are more likely to develop Alzhemier's disease than smokers. Assuming these investigations were carefully carried out, what is the most reasonable conclusion?
These were probably observational studies, and so no conclusion about smoking providing protection against Alzheimer's is proper. (b.)
Ch. 3 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 xbar = 8.4, sx = 2.1, ybar = 14.2, sy =3.8, and r= 0.86. What is the slope of the least-squares regression line of number of service calls on number of copiers?
1.56 (b.)
Ch.3 A fisheries biologist studying whitefish in a Canadian Lake collected data on the length (in centimeters) and egg production for 25 female fish. A computer regression analysis of egg production versus fish length are given below. Note that number of eggs is given in the thousands (i.e., "40 means 40,000 eggs)
6.751 (c.)
Ch.4 Mrs. Lennard conduction a survey in the city of Tampa to estimate the proportion of cars that are red. A simple sample of 25 cars from a parking lot at her school, Red Eagle High School, was selected. Which of the following statements is correct?
A different individual, doing the sampling independently, would probably obtain a slightly different answer for their sample proportion .
Ch.3 (corrected) One characteristic of roller coasters that contribute to the maximum speed of the ride is the track's maximum height (in feet) for nine roller coasters that opened recently around the world. Which of the following best describes what S=10.537 represents in this setting?
This represents the standard deviation of residuals (d.)
Ch.4 Cardiologists at Athens medical school in Greece wanted to test whether chocolate affected blood flow in the blood vessels. the researchers recruited 17 healthy young volunteers, who were each given a 3.5 oz bar of dark chocolate, either Bittersweet or fake chocolate. on another day, the volunteers have switched the subjects had no chocolate outside the study, and investigators didn't know whether a subject had eaten a real or fake chocolate. an ultrasound was taken of each volunteer's upper arm to see the functioning of the cells in the walls of the main artery. the investigators found that blood vessel function was improved when the subjects ate bittersweet chocolate and that there were no such changes when the eighth placebo This research was
a matched pairs experiment (a.)
Ch.4 A news release for a diet Product Company reports" we have good news for the 65 million Americans currently on a diet". its sudy showed that people who lose weight can keep it off. the sample consisted of 20 graduates of the company's program who endorsed it in commercials. the results of the study are probably
biased, overstating the effectiveness of the diet (a.)
Ch.4 Does caffeine improve exam performance? Suppose all students in the 8:30 section of a course are given a "treatment" ( two cups of coffee) and all students in the 9:30 section are not permitted to have any caffeine before a midterm. Unfortunately, any systematic difference between the two sections on the exam might be due to the fact that the 8:30 and 9:30 classes have different instructors. This is an example of
confounding (a.)
Ch.3 The following scatter plot present 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.
countries that drink more wine have lower death rates from heart disease (c.)
Ch.3 Consider the following scatter plot 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.
has a negative value for the residual (a.)
Ch.4 Fizz Laboratories, a pharmaceutical company has developed a new drug for relieving cronic pain. Sixty patients suffering from arthritis and needing pain relief are available. Each patient will be treated and asked an hour later, "About what percent of pain relief did you experience?" From this information, you conclude:
nothing, because there is no control group for comparison. (d.)
Ch. 3 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 scatter plot was constructed. If heart disease death rate were expressed as death per 1,000 people instead of as deaths per 100,000 people, how would the correlation r between wine consumption and heart disease death rate change?
r would not change (c.)
Ch. 3 The following scatter plot presents data on wine consumption (in liters per person per year) in 19 developed western countries.
r=-0.84 (a.)
Ch.4 A sales representative wishes to survey her client bas of 47 companies. She has 47 business cards, all of them identical in size, from her contacts in the companies, and decides to drop them all in a small box, shake them up, and reach in to pick 5 cards for her sample. This procedure is an example of which type of sampling?
simple random sample (b.)
Ch. 3 A community college announces that the correlation between college entrance exam grades and scholastic achievement was found to be -1.08. Based upon this you would tell the college that ....
the college should hire a new statistician (e.)
Ch.3 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 the liters of alcohol per person?
the mean, the first quartile, and the variance of wine consumption (a.)
Ch.4 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 (homogeneous) within the groups but different (heterogeneous) between groups. (c.)
Ch.3 A study of child development measures the age (in months) at which a child begins to talk and the child's score on ability test given several years later. The study asks whether the age at which a child talks helps predict the later test score. The least-squares regression line useful for predicting test scores from age is yhat= 110 - 1.3x. According to this regression line, what happens (on the average) to children who talk one month later than other children?
their predicted tests score goes down 1.3 points (b.)
Ch.3 Below is a scatter plot (with the least-squares regression line) for calories and protein (in grams) in one cup of 11 varieties of dried beans. The computer output for this regression is below the plot.
we can predict that the protein content for soybeans is 55.4 grams (a.)
Ch. 3 (corrected) If bi-variate data set A has a correlation r= 0.95, and a second variate data set B has a correlation r= -0.95, then ...
you can't tell whether either data set is best described by a linear model until you examine the scatterplots. (d.)
Ch.3 We measure a response variable y at several different times. A residual plot of log y versus time of measurement is created to determine if an exponential model is appropriate to model the relationship between time and the response variable. The residual plot displays random scatter about the line residual = 0. Which one of the following conclusions can be made?
The model is appropriate because the residual plot displays random scatter about the line residual = 0