Sampling & Experimental Design Review

Can pleasant aromas help a student learn better? Two researchers believed that the presence of a floral scent could improve a person’s learning ability in certain situations. They had 22 people work through a pencil-and-paper maze six times, three times while wearing a floral-scented mask and three times wearing an unscented mask. The three trials for each mask closely followed one another. Testers measured the length of time it took subjects to complete each of the six trials. They reported that, on average, subjects wearing the floral-scented mask completed the maze more quickly than those wearing the unscented mask, although the difference was not statistically significant. This study is

• a convenience sample 
• an observational study, not an experiment
• an experiment, but not a double-blind experiment 
• a double-blind experiment

A marketing research firm wishes to determine if the adult men in Laramie, Wyoming, would be interested in a new upscale men’s clothing store. From a list of all residential addresses in Laramie, the firm selects a simple random sample of 100 and mails a brief questionnaire to each. The population of interest is

• all adult men in Laramie, Wyoming 
• all residential addresses in Laramie, Wyoming
• the members of the marketing firm that actually conducted the survey
• the 100 addresses to which the survey was mailed

Twelve people, who suffer from chronic fatigue syndrome, volunteer to take part in an experiment to see if, shark fin extract will increase one’s energy level. 8 of the volunteers are men and 4 are women. Half of the volunteers are to be given shark extract twice a day and the other half a placebo twice a day. We wish to make sure that 4 men and 2 women are assigned each of the treatments, so we decide to use a block design with the men forming one block and the women the other.

Suppose the researchers decide to bring in a doctor who is responsible for determining if a subject displays an increase in energy level. In this case, we should probably

• use two placebos 
• use stratified sampling to assign subjects to treatments
• use fewer subjects but observe them more frequently 
• conduct the study as a double-blind experiment

The SDSU Student Union wants to know what type of events students are interested in so they decide to get a sample of undergraduate students. Which of the following would be the least useful variable to stratify by?

• major
• whether or not a student lives on or off campus
• grade level
• whether or not they drink coffee

A study of the effects of running on personality involved 231 male runners who each ran about 20 miles a week. A news report (New York Times, Feb. 15, 1988) stated, “The researchers found statistically significant personality differences between the runners and the 30-year-oldmale population as a whole.” A headline on the article said, “Research has shown that running can alter one’s moods.” Which of the following statements about the study is true?

• It was not a designed experiment 
• It was an experiment, but not a double-blind experiment
• It was a double-blind experiment, but not a randomized 
• It was a randomized, double-blind experiment

One hundred volunteers who suffer from severe depression are available for a study. Fifty are selected at random and are given a new drug that is thought to be particularly effective in treating severe depression. The other 50 are given an existing drug for treating severe depression. A psychiatrist evaluates the symptoms of all volunteers after four weeks in order to determine if there has been substantial improvement in the severity of the depression.
The study described above would be double-blind if

• neither drug had any identifying marks/labels on it
• all volunteers were not allowed to see the psychiatrist nor the psychiatrist allowed to see the volunteers during the session during which the psychiatrist evaluated the severity of the depression
• neither the volunteers nor the psychiatrist knew which treatment any person had received
• all of the above

One hundred volunteers who suffer from severe depression are available for a study. Fifty are selected at random and are given a new drug that is thought to be particularly effective in treating severe depression. The other 50 are given an existing drug for treating severe depression. A psychiatrist evaluates the symptoms of all volunteers after four weeks in order to determine if there has been substantial improvement in the severity of the depression.

Suppose volunteers were first divided into men and women, and then half of the men were randomly assigned to the new drug and half of the women were assigned to the new drug. The remaining volunteers received the other drug. This would be an example of

• replication
• confounding
• block design
• matched pairs design

A public opinion poll in Ohio wants to determine whether registered voters in the state approve of a measure to ban smoking in all public areas. They select a simple random sample of 50 registered voters from each county in the state and ask whether they approve or disapprove of the measure. What type of sample would this be?

• systematic
• stratified
• simple random
• convenience

An amateur gardener decides to change varieties of tomatoes for this year to see if the yield is improved. He puts 6 of the old type of tomato plants and 6 of the new tomato plants in his garden. The average yield for the old plants was 11.3 pounds and the average for the new plants was 14.5 pounds. This is an example of

• an experiment
• an observational study

A television station is interested in predicting whether voters in its viewing area are in favor of federal funding for abortions. It asks its viewers to phone in and indicate whether they support/are in favor of or are opposed to this. Of the 2241 viewers who phoned in, 1574 (70.24%) were opposed to federal funding for abortions.
This method of sampling likely suffered from...

• undercoverage
• voluntary response bias
• response bias
• non-response bias