Homework #5-Chapter8&9&4 (20pts for turned in on time) 4. (12pts)Of the followin

Question

Homework #5-Chapter8&9&4 (20pts for turned in on time) 4. (12pts)Of the following study, first identify what kind of study it is (observational study or experiment), then point out the explanatory variable and response variable (1) (3pts)The relationship between healthy diet and prevalence of cataracts was assessed using a sample of 1808 participants. They asked these people what kind of diet they generally have during the day, and relates to what conditions they have in terms of cataracts. (2) (3pts)As men age, their testosterone levels gradually decrease. This may cause a reduction of lean body mass, an increase in fat and other undesirable changes. A researcher wants to know if testosterone supplements reverses some of these effects. In the study, there were 237 participants with low testosterone level of similar age. Some of the participants were asked to take testosterone supplements daily for a month, while the rest were asked to take placebo pills daily for a month None of the participants knew which pills they were asked to take. Their testosterone levels were tested again after a month (3) (3pts)A psychologist wants to know if the difficulty of a task influences people estimate of how long they spend working on it. She designs two sets of mazes that subjects can work through on computers. One set is easy and the other set is difficult. She has 30 students with similar age and physical condition to participate. Of the 30 students, she randomly selected 15 to work on the easy set, and the other 15 work on the difficult set. After some time, she tells them to stop and asks them how much time they have spent. (4) (3pts)A study surveyed 1,434 people, asking their physical condition and how often and how much they drink alcohol from an online survey tool. The study showed that those who drink moderately has the best physical condition comparing with those who drink heavily or don't drink alcohol at all. 5. (4pts)You are using a random digits table to choose a simple random sample of 6 students fronm a class of 50 students. The students are labeled as 01, 02, 03,..., 49, 50. Which of the following is a possible sample that you can obtain? (no need to read the random digits table) A. 45, 74, 04, 18, 07, 45 B. 45, 04, 18, 07, 45, 19 C. 45, 04, 18, 07, 19, 20 D. 45, 04, 18, 07, 19, 00

Explanation / Answer

4(1)

Here reseacher did not give any treatment to any participants. He/she only observed the participants diet.

Hence, it is observational study.

Explanatory variable: Type of diet

Response variable: Prevalance of cataracts

(2)

Here reseacher assigned treatments to some participants.

Hence, it is experimental study.

Explanatory variable: Type of treatment: placebo or pills

Response variable: level of testosterone

(3)

Here reseacher assigned treatments (difficult maze and for some easy maze) to some participants.

Hence, it is experimental study.

Explanatory variable: Type of treatment: easy amze, difficult maze

Response variable: time spent

(4)

Here reseacher did not give any treatment to any participants. He/she only observed the participants diet.

Hence, it is observational study.

Explanatory variable: Drinking alcohol

Response variable: Physical condition

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