AP Stat - semester 1
In an AP stats class, 52% of students eat breakfast in the morning and 40% of students floss their teeth. Twenty-six percent of students eat breakfast and also floss their teeth. What is the probability that a student from this class eats breakfast or flosses their teeth?
.52+.40-.26=66%
the correlation coefficient between high school grade point averages and college GPA is .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 _____ the mean
.560(2.5) = 1.4
a residuals plot is useful because 1) it might show a pattern in the data that was hard to see in the original scatterplot 2) it will clearly identify influential points 3) it will help us to see whether our model is appropriate
1) it might show a pattern in the data that was hard to see in the original scatterplot 3) it will help us to see whether our model is appropriate
the model square root predicted str = 12 + 20dia can be used to predict the breaking strength of a rope (in pounds) from its diameter (in inches). According to this model, how much force should a rope 1 inch diameter
1024 lbs
the ages of people attending the opening show of a new movie are summarized in the ogive shown. estimate the IQR of the ages. Q1 = 29 Q3=43
12
the standard deviation of the data displayed in this dotplot is most likely to be
12
a poll of 120 ithacans found that 30 had visited the museum of the earth, and that 80 had been to home depot. If it appeared that going to home depot and going to the museum of the earth were independent events, how many of those polled had been to both x/30 = 80/120
20
Batco. a company that sells batteries claims that 99.5% of their batteries are in working order. How many batteries would you expect to buy, on average, to find one that does not work?
200
what is the probability that a student from this class eats breakfast but does not floss their teeth
26%
some marathons allow two runners to "split" the marathon by each running a half marathon. Alice and Sharon plan to split a marathon. Alice's half-marathon times average 92 minutes with a standard deviation of 3 minutes and sharon half-marathon times average 96 minutes with a standard deviation of 1 minutes. Assume that the women's half-marathon times are independent. The expected time for Alice and Sharon to complete a full marathon 92+96=188 minutes. What is the standard deviation of their total time? square root 3^2+1^2
3 minutes
a basketball player has a 70% fee throw percentage. Which plan could be used to simulate the number of free throws she will make in her next five free throw attempts> 1) let 0,1 represent making the first shot 2,3 represent making the second shot... 8,9 represent making the fifth shot. Generate five random numbers 0-9 ignoring repeats 2) 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 ignoring repeats 3) let 0,1,2 represent missing a shot 3,4,...9 represent making a shot. Generate five random numbers 0-9 and how count how many numbers 3-9
3 only
the regression analysis of students' college grade point averages and their high school GPAs found r^2=.311. Which of these is true 1) 31.1% of college GPAs can be correctly predicted with this model 2) 31.1% of the variance in college GPA can be accounted for by the model 3) high school GPA accounts for 31.1% of college GPA
31.1% of the variance in college GPA can be accounted for by the model
five juniors and three seniors have applied for two open student council positions. School administrators have decided to pick the two new members randomly. What is the probability they are both juniors or both seniors?
5/8(4/7) + 3/8(2/7) = .4643
A fair coin has come up "heads" 10 times in a row. The probability that the coin will come up heads on the next flip is
50%
two sections of a class took the same quiz. Section A had 12 students who had a mean score of 60 and section B had 20 students who had a mean score of 85. Overall, what was the approximate mean score for all of the students on the quiz
75.6
Two variables that are actually not related to each other may nonetheless have a very high correlation because they both result from some other, possibly hidden, factor. This is an example of
a lurking variable
environmental researchers 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
a timeplot
which of the following is not a source of caution in regression analysis between two variables a) extrapolation b) lurking variable c) an outlier d) subgroups with different characteristics
all of the above
in an experiment the primary purpose of blinding is to reduce
bias
According to the national telecommunication and information administration 50.5% of US households had internet access in 2001. What is the probability that four randomly selected US households all had internet access in 2001?
binompdf(4, .505, 4) 6.5%
placebos are a tool for
blinding
if we wish to compare the average PSAT scores of boys and girls taking AP stat at this high school, which would be the best way to gather these data
census
the correlation coefficient between the hours that a person is awake during a 24-hour period and the hours that same person is asleep is during a 24-hour period is most likely to be
exactly -1.0
school administrators collect data on students attending the school. Which of the following variables is quantitative
grade point average
we collect these data from 50 male students. Which variable is categorical a) foot length b) hair color c) GPA d) number of books read in the last month e) number of TV sets at home
hair color
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 two events are most likely to be independent a) having a driver's license, and having blond hair b) being a senior, and taking college classes c) having a flat tire, and being late for school d) having a car accident, and having 3 inches of snow today e) getting an A in math, and getting an A in physics
having a driver's license and having blond hair
suppose that a normal model described student scores in a history class. Parker has a standardized score of +2.5 this means that Parker
is 2.5 standard deviation above average for the class
which of the following data summaries are changed by adding a constant to each data 1) the standard deviation 2) the mean 3) the median
mean and median
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 no 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 researchers installed the NAPA battery and repeated the test. Is this a good experimental design?
no, because the temperature is confounded by brand
according to the national telecommunication and information adminstration 43.5% of US households owned a computed in 2001. What is the probability that of three randomly selected US households at least one owned a computer in 2001?
p(at least one) = p(none) p(x>1) = 1-binomcdf(3, .435, 0) = .82%
what is the probability there is exactly 1 jumbo among the first 6 cones sold by the ice cream stand?
p(x=1) binompdf(6, .12, 1) = 38%
an ice cream stand reports that 12% of the cones they sell are jumbo size. You want to see what a jumbo cone looks like, so you can stand and watch the sales for a while. What is the probability that the first jumbo cone is the fourth cone you see them sell
p(x=4) geometpdf(.12,4) = 8%
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
pie chart
when using midterm exam 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
does regular exercise decrease the risk of cancer? a researcher finds 200 women over 50 who exercise regularly, pairs each with a woman who has similar medical history but does not exercise, then follows the subjects for 10 years to see which group develops more cancer. this is a
prospective study
more dogs are being diagnosed with thyroid problems than have been diagnosed in the past. A researcher 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 1) randomization in assigning subjects to treatments 2) blinding the participants to the treatments 3) replication of the experiment on a sufficient number of subjects
randomization in assigning subjects to treatments, blinding the participants to the treatments, and replication of the experiment on a sufficient number of subjects
twenty dogs and 20 dogs 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
randomized block, blocked by species
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 date
sample survey
all but one of the statements below contain a mistake. Which one could be true? a) the correlation between weight and length of foot is 0.488 pounds per inch b) the correlation between height and weight is .568 c) if the correlation between blood alcohol level and reaction time is .73 then the correlation between reaction time and blood alcohol is -.73 d) the correlation between gender and age is -.171 e) the correlation between the breed of a dog and its weight is .435
the correlation between height and weight is .568
residuals are
the difference between observed responses and values predicted by the model
which is true of the data whose distribution is shown 1)the distribution is skewed to the right 2) the mean is probably larger than the median 3) we should summarize with median and IQR
the distribution is skewed to the right, the mean is probably larger than the median, and we should summarize with median and IQR
double blinding in experiments is important so that 1) the evaluators do not know which treatment group the participants are in 2) the participants do not know which treatment group they are in 3) no one knows which treatment any of the participants are getting
the evaluators do not know which treatment group the participants are in and the participants do not know which treatment group they are in
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? 1) the population of interest is all potential car buyers 2) this survey design suffered from non-response bias 3) because it comes from a sample 44% is a parameter, not a statistic
the population of interest is all potential car buyers this survey design suffered from non-response bias
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 and to the correlation
the slope of the line of best fit will increase, and the correlation will decrease
the five number summary of credit hours for 24 students in a statistic class is: fences Q1-1.5(IQR) Q3+1.5(IQR)
there are no outliers in the data
a correlation of zero between two quantitative variable means that
there is no linear association between the two variables
which of the following variables would most likely follow a normal model a) family income b) all of these c) heights of singes in a co-ed choir d) scores on an easy test e) weights of adult male elephant
weights of adult male elephant
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 each students is equally likely to be chosen
