Answer the following questions and submit for grading. Each question or part of a question is worth 1 point.
1. Researchers asked a sample of 50 1st grade teachers and a sample of 50 12th grade teachers how much of their own money they spent on school supplies in the previous school year. They wanted to see if teachers at one grade level spend more than teachers at the other grade level.
a. What type of study is found—observational or randomized experiment? Explain.
b. What is the experimental (or observational) unit?
c. What is the response variable?
d. What is the explanatory variable?
e. Do we have to worry about confounding variables in this instance? Why? If so identify a possible confounding variable?
f. Are either of the terms retrospective study or prospective study relevant? Explain.
2. A research team compared two methods of measuring tread wear on tires. Eleven tires were each measured for tread wear by two different methods: one method was based on weight while the other method was based on groove wear. For convenience, each tire was measured first by weight method and then second by the groove wear.
a. The two samples are which of the following: two independent or two dependent (matched pairs)? Explain.
b. What type of study is found—observational or randomized experiment? Explain.
c. What is the experimental (or observational) unit?
d. What is the response variable?
e. What is the explanatory variable?
3. A study wants to determine if taking fish oils can reduce depressive symptoms. A group of 50 volunteers who suffered from mild depression were randomly divided into two groups. Each person was given a three-month’s supply of capsules. One group was given capsules that contained fish oils while the other group was given capsules that look and tasted like fish oils, but actually only contained sugar. Neither the participants nor the investigator knew what type of capsule they were taking. At the end of the month, a psychologist…