a p s t a t s -- m u l t i p l e c h o i c e
the veterinary bills for the dogs are summarized in the ogive below. estimate the iqr of these expenses
$100
education research consistently shows that students from wealthier families tend to have higher sat scores. the slope of the line that predicts sat score from family income is 6.25 points per $1000, and the correlation between the variables is 0.48. then the slope of the line that predicts family income from sat score (in $1000 per point)?
0.037
the correlation between x and y is r = 0.35. if we double each x value, decrease each y by 0.20, and interchange the variables (put x on the y axis and vice versa), the new correlation?
0.35
the auto insurance industry crashed some test vehicles into a cement barrier at speeds of 5 to 25 miles per hour to investigate the amount of damage to the cars. they found a correlation of r = 0.60 between speed (mph) and damage ($). if we speed at which a car hit the barrier is 1.5 standard deviations above the mean speed, we expect the damage to be _____ the mean damage
0.90 sd above
the correlation coefficient between high school grade point average (gpa) and college gpa is 0.560. for a student with a high school gpa that is 2.5 standard deviations above the mean, we would expect that student to have a college gpa that is?
1.4 sd above
the standard deviation of the data displayed in this dot plot is most likely to be?
12
the ages of people attending the opening show of a new movie are summarized in the ogive shown. estimate the iqr of the ages?
13
the best estimate of the standard deviation of the mens' weights displayed in this dot plot is?
25
a regression analysis of students' college grade point averages (gpas) and their high school gpas found r2 = 0.311. which of these is true?
31.1% of the variance in college gpa can be accounted for by the model
the model sq rt distance = 3.30 + 0.235(speed) can be used to predict the stopping distance (in feet) for a car traveling at a specific speed (in mph). according to this model, about how much distance will a car going 65 mph need to stop?
345.0 feet
last weekend police ticketed 18 men whose mean speed was 72 miles per hour, and 30 women going an average of 64 miles per hour. overall, what was the mean speed of all the people ticked?
67 mph
the mean number of hours worked for the 30 males was 6, and for the 20 females was 9. the overall mean number of hours worked?
7.2
a consumer group collected information on hdtv's. they created a linear model to estimate the cost of an hdtv (in $) based on the screen size (in inches). which is the most likely value of the slope of the line of best fit?
70
two sections of a class took the same quiz. section a had 15 students who had a mean score of 80, and section b had 20 students who had a mean score of 90. overall, what was the approximate mean score for all of the students on the quiz?
85.7
it's easy to measure the circumference of a tree's trunk, but not so easy to measure its height. foresters developed a model for ponderosa pines that they use to predict the tree's height (in feet) from the circumference of its trunk (in inches): lnh = -1.2 +1.4(ln c). a lumberjack finds a tree with a circumference of 60"; how tall does this model estimate the tree to be?
93'
two variables that are actually not related to each other may nonetheless have a very high correlation because they both result from some other, possible hidden factor. this is an example of?
a lurking variable
a medical researcher finds that the more overweight a person is, the higher his pulse rate tends to be. in fact, the model suggests that 12 pound differences in weight are associated with differences in pulse rate of 4 beats per minute. which is true?
a positive residual means a person's pulse rate is higher than the model predicts
suppose that a normal model describes fuel economy (miles per gallon) for automobiles and that a saturn has a standardized score (z-score) of +2.2. this means that saturns?
achieve fuel economy that is 2.2 standard deviations better than the average car
which of the following is not a goal of re-expressing data?
all of these are goals of re-expressing data
which of the following is not a source of caution in regression analysis between two variables?
all of these are potential problems
if the point in the upper right corner of this scatterplot is removed from the data set, then what will happen to the slope of the line of best fit (b) and to the correlation (r)?
b will decrease, and r will increase
in an experiment the primary purpose of blinding is to reduce?
bias
which statement about bias is true?
bias results from a sampling method likely to produce samples that do not represent the population
places are a tool for?
blinding
which of the following is not required in an experimental design?
blocking
if the point in the upper left corner of the scatterplot is removed, what will happen to the correlation (r) and the slope of the line of best fit (b)?
both will increase
if we want to discuss any gaps and clusters in a data set, which of the following should not be chosen to display the data set?
boxplot
the spca collects the following data about the dogs they house. which data is categorical?
breed
we wish to compare the average ages of the math and science teachers at your school. which is the best way to collect the data?
census
which scatterplot shows a strong association between the two variables even though the correlation is probably near 0?
downwards parabola
the correlation coefficient between the hours that a person is awake during 24 hour period and the hours that same person is asleep during a 24 hour period is most likely to be?
exactly -1.0
although there are annual ups and downs, over the long run, growth in the stock market averages about 9% per year. a model that best describes the value of a stock portfolio is probably?
exponential
another company's sales increase by the same percent each year. this growth is?
exponential
which of the following variables would most likely follow a normal model?
family income
school administrators collect data on students attending the school. which of the following variables is quantitative?
grade point average
suppose that a normal model describes the acidity (ph) of rainwater, and that water tested after last week's storm had a z-score of 1.8. this means that the acidity of that rain?
had a ph 1.8 standard deviations higher than that of average rainwater
a researcher wants to compare the performance of three types of pain relievers in volunteers suffering from arthritis. because people of different ages may suffer arthritis of varying degrees of severity, the subjects are split into two groups: under 60 and over 60. subjects in each group are randomly assigned to take one of the medications. twenty minutes later they rate their levels of pain. this experiment?
has one factor (medication) blocked by age
a researcher wants to compare the effect of a new type of shampoo on hair condition. the researcher believes that men and women may react to the shampoo differently. additionally, the researcher believes that the shampoo will react differently on hair that is dyed. the subjects are split into four groups: men who dye their hair; men who do not dye their hair; women who dye their hair; women who do not dye their hair. subjects in each group are randomly assigned to the new shampoo and the old shampoo. this experiment?
has one factor (shampoo type), blocked by gender and whether hair is dyed
which of those variables is most likely to follow a normal model?
head circumference
the correlation between a family's weekly income and the amount they spend on restaurant meals is found to be r = 0.30. which must be true?
in general, the higher the income, the more the family spends in restaurants
suppose that a normal model described student scores in a history class. parker has a standardized score (z-score) of +2.5. this means that parker?
is 2.5 standard deviations above average for the class
a residuals plot is useful because?
it will help us to see whether our model is appropriate it might show a pattern in the data that was hard to see in the original scatterplot
among a dozen eggs, three are rotten. a cookie recipe calls for two eggs; they'll be selected randomly from that dozen. which plan could be used to simulate the number of rotten eggs that might be chosen?
let 0, 1 and 2 represent the rotten eggs, and 3, 4 .. 11 the good eggs. generate two random numbers 0-11, ignoring repeats
a basketball player has a 70% free throw percentage. which plan could be used to simulate the number of free throws she will make in her next five free throw attempts?
let 0, 1, 2 represent missing a shot and 3, 4 ... 9 represent making a shot. generate five random numbers 0-9 and count how many numbers are in 3-9
a company's sales increase by the same amount each year. this growth is?
linear
over the past decade a farmer has been able to increase his wheat production by about the same number of bushels each year. his most useful predictive model is probably?
linear
researchers studying growth patterns of children collect data on the heights of fathers and sons. the correlation between the fathers' heights and the heights of their 16 year old son is most likely to be?
near +0.7
suppose the state decides to randomly test high school wrestlers for steroid use. there are 16 teams in the league, and each team has 20 wrestlers. state investigators plan to test 32 of these athletes by randomly choosing two wrestlers from each team. si this a simple random sample?
no because not all possible groups of 32 wrestlers could have been the sample
to check the effect of cold temperatures on the battery's ability to start a car, researchers purchased a battery from sears and one from napa. they disabled a car so it would not start, put the car in a warm garage, and installed the sears battery. they tried to start the car repeatedly, keeping track of the total time that elapsed before the battery could not longer turn the engine over. then they moved the car outdoors where the temperature was below zero. after the car had chilled there for several hours, the researches installed the napa battery and repeated the test. is this a good experiment design?
no because temperature is confounded by brand
a regression analysis of company profits and the amount of money the company spent on advertising found r2 = 0.72. which of these is true?
none
suppose a normal model describes the number of pages printer ink cartridges last. if we keep track of printed papes for the 47 printers at a company's office, which must be true?
none
which is true?
none
your stats teacher tells you your test scored was the 3rd quartile for the class. which is true?
none of these
when using midterm scores to predict a student's final grade in a class, the student would prefer to have a?
positive residual, because that means the student's final grade is higher than we would predict with the model
the advantage of making a stem and leaf display instead of a dotplot is that a stem and leaf display?
preserves the individual data values
a researcher identified 100 men over forty who were not exercising and another 100 men over forty with similar medical histories who were exercising regularly. she followed the men for several years to see if there were any difference between the groups in the rate of heart attacks. this is a?
prospective study
more dogs are being diagnosed with thyroid problems than have been diagnosed in the past. a researched identified 50 puppies without thyroid problems and kept records of their diets for several years to see if any developed thyroid problems. this is a?
prospective study
which is important in designing a good experiment?
randomization in assigning subjects to treatments control of potentially confounding variables replication of the experiment on a sufficient number of subjects
twenty dogs and twenty cats were subjects in an experiment to test the effectiveness of a new flea control chemical. ten of the dogs were randomly assigned to an experimental group that wore a collar containing the chemical, while the others wore a similar collar without the chemical. the same was done with the cats. after 30 days the veterinarians were asked to inspect the animals for fleas and evidence of flea bites. this experiment is?
randomized block, blocked by species
which statement about correlation is true?
regression based on data that are summary statistics tends to result in a higher correlation
which statement about influential points is true?
removal of an influential point changes the regression line data points that are outliers in the horizontal direction are more likely be influential than points that are outliers in the vertical direction
we might choose to display data with a stemplot rather than a boxplot because a stemplot?
reveals the shape of the distribution displays the actual data
a company sponsoring a new internet search engine wants to collect data on the ease of using it. which is the best way to collect the data?
sample survey
which is true about sampling?
sampling error is usually reduced when the sample size is larger sampling error is the result of random variations and is always present
all but one of these statements contains a mistake. which could be true?
the correlation between the amount of fertilizer used and the yield of beans is 0.42
all but one of the statements below contain a mistake. which one could be true?
the correlation between weight and length of foot is 0.488
residuals are?
the difference between observed responses and values predicted by the model
which is true of the data shown in the histogram?
the distribution is approximately symmetric the mean and median are approximately equal
which is true of the data whose distribution is shown?
the distribution is skewed to the right
double blinding in experiments is important so that?
the evaluators do not know which treatment group the participants are in the participants to not know which treatment group they are in
a least squares line of regression has been fitted to a scatterplot; the model's residuals plot is shown. which is true?
the linear model is appropriate
which of the following data summaries are changed by adding a constant to each data value?
the mean the median
which is true of the data shown in the histogram?
the mean is probably smaller than the median we should use median and iqr to summarize these data
the owner of a car dealership planned to develop strategies to increase sales. he hoped to learn the reasons why many people who visit his car lot do not eventually buy a car from him. for one month he asked his sales staff to keep a list of the names and addresses of everyone who came in to test drive a car. at the end of the month he sent surveys to the people who did not buy the car, asking them why. about one third of them returned the survey, with 44% of those indicating that they found a lower price elsewhere. which is true?
the population of interest is all potential car buyers this survey design suffered from non response bias
the january 2005 gallup youth survey telephoned a random sample of 1028 u.s teens and asked these teens to name their favorite movie from 2004. napoleon dynamite had the highest percentage with 8% of teens ranking it as their favorite movie. which is true?
the population of interest is all u.s teens 8% is a statistic and not the actual percentage of all u.s teens who would rank this movie as their favorite this sampling design should provide a reasonably accurate estimate of the actual percentage of all u.s teens who would rank this movie as their favorite
hoping to get information that would allow them to negotiate new rates with their advertisers, natural health magazine phoned a random sample of 600 subscribers. 64% of those polled said they use nutritional supplements. which is true?
the population of interest is the people who read this magazine this sampling design should provide the company with reasonably accurate estimate of the percentage of all subscribers who use supplements
a scatterplot of 1/sq rt y vs. x shows a strong positive linear pattern. it is probably true that?
the residuals plot for regression of y and x shows a curved pattern
the five number summary of credit hours for 24 students in a statistics class is?
there are no outliers in the data
a correlation of zero between two quantitative variables means that?
there is no linear association between the two variables
a professor has kept records on grades that students have earned in his class. if he wants to examine the percentage of students earning the grades a, b, c, d and f during the most recent term, which kind of plot could he make?
timeplot
environmental researches have collected rain acidity data for several decades. they want to see if there is any evidence that attempts to reduce industrial pollution have produced a trend toward less acidic rainfall. they should display their data in?
timeplot
the spca has kept these data records for the past 20 years. if they want to show the trend in the number of dogs they have housed, what kind of plot should they make?
timeplot
a chemistry professor who teaches a large lecture class surveys his students who attend his class about how he can make the class more interesting, hoping he can get more students to attend. this survey method suffers from?
undercoverage
in an experiment the primary purpose of blocking is to reduce?
variation
which variable about german shepherds is most likely to be described by a normal model?
veterinary cost
suppose your local school district decides to randomly test high school students for attention deficit disorder (add). there are three high schools in the district, each with grades 9-12. the school board pools all of the students together and randomly samples 250 students. is this a simple random sample?
yes because they could have chosen any 250 students from throughout the district
