AP Statistics Two Categorical Variables and Two-Way Tables Quiz: 10 Questions with Explanations

A 30%B 50%C 60%D 40%

Among the 50 boys, 30 own a pet, so 30/50 = 60%. 30% is the joint percent of all 100 students.

A No associationB A strong associationC Group 1 is largerD Group 2 causes yes answers

The conditional percents are identical, so knowing the group tells nothing about the answer.

A MarginalB JointC ConditionalD Cumulative

A joint relative frequency uses the grand total. Conditional divides by a group total.

A 40%B 33.3%C 66.7%D 25%

Y has 40 + 20 = 60 individuals and 40 are in A, so 40/60 = 66.7%.

A Compare percents of the response within each explanatory groupB Compare cell counts onlyC Compare marginal totals onlyD Compare the grand total

Raw counts depend on group size, so compare conditional percents.

A a table has too many cellsB the data are quantitativeC a sample is not randomD a trend reverses after splitting the data by a lurking variable

Combined results can differ from subgroup results because group sizes differ.

A the mean of each groupB the correlationC the medianD conditional distributions of the response for each explanatory group

Each bar is one group and the segments are its conditional percents, which add to 100%.

A 50%B 25%C 4%D 75%

50/200 = 0.25. A common error is to divide by the number of cells.

A one causes the otherB the variables are associated, but not necessarily causallyC the sample is biasedD there is no relationship

Only a randomized experiment supports causation.

A Smokers have asthma at 30% compared with 15% for nonsmokersB Nonsmokers have more asthma because 18 is greater than 12C Both groups have the same percentD Smokers have asthma at 12%

Compare percents: 12/40 = 30% and 18/120 = 15%. The larger count belongs to the larger group.