Unit 3 · Test
Unit 3 test: Collecting Data
14 questions. Answer them all, then submit to see your score. Solutions unlock after you submit.
This test covers sampling methods, bias in sampling, observational studies and experiments, experimental design, and the scope of inference.
A hospital wants to survey its staff about a new scheduling system. It separates the staff into nurses, doctors and support staff, then selects an SRS of 25 people from each group. What type of sample is this?
A community pool has 900 members: 540 adults, 270 teens and 90 children. The manager selects a stratified random sample of 50 members with proportional allocation by age group. How many teens should be in the sample?
Enter a number. Fractions like 3/4 and sqrt(2) are OK.
An airline wants to estimate customer satisfaction on a particular day. It randomly selects 6 of that day's 70 flights and surveys every passenger on those 6 flights. Which statement is true?
A factory produces 2,500 light bulbs in a shift and wants a systematic random sample of 50 bulbs for quality testing. After a random start among the first bulbs, every th bulb will be tested. What should be?
Enter a number. Fractions like 3/4 and sqrt(2) are OK.
A video game company posts a link on its forums asking players to rate a new update. Of the 4,000 players who respond, 65% rate it "poor." Which statement best describes this result?
A town selects an SRS of 500 households from its utility billing records to survey about recycling. Many of the selected households never return the survey. Separately, households in a new apartment complex are not yet in the billing records. Which pair of labels is correct?
A researcher randomly selects 1,250 residents and mails each a survey. 350 surveys are returned. What is the response rate, as a percent?
Enter a number. Fractions like 3/4 and sqrt(2) are OK.
Which of these is an experiment?
An observational study finds that teenagers who play competitive sports have higher self-esteem scores than teenagers who don't. Which is the best example of a possible confounding variable, with an explanation?
An engineer tests how tire pressure (4 levels) and road surface (asphalt, concrete, gravel) affect stopping distance. She wants 5 test runs for each treatment, using a different car for each run. How many cars does she need?
Enter a number. Fractions like 3/4 and sqrt(2) are OK.
A researcher testing two memory-training programs divides 100 subjects into an under-40 group and a 40-and-older group, because age is expected to affect memory. Within each age group, she randomly assigns half of the subjects to each program. What design is this?
A study of two nicotine-free stress-relief gums and a placebo gum has 72 subjects: 30 smokers and 42 nonsmokers. The researchers block by smoking status and, within each block, split subjects equally among the 3 treatments. How many nonsmokers receive each treatment?
Enter a number. Fractions like 3/4 and sqrt(2) are OK.
In a test of a new allergy spray, patients are randomly assigned to the spray or a saltwater spray that looks and smells the same. The patients don't know which spray they received, but the doctors who rate their symptoms do know. Which statement is correct?
A researcher randomly selects 200 of the 3,000 members of a statewide teachers' association. She randomly assigns half of them to complete an online mindfulness course, and the other half do not. After 8 weeks, the course group reports significantly lower stress. Which conclusion is justified?