Question: 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 evaluated them to determine if their depressive symptoms had changed. Therefore, we are comparing the "change in depressive symptoms" for these individuals in the two groups. Explain whether each of the following terms applies to this study.
a. observational study
b. randomized experiment
c. placebo
d. placebo effect
e. single-blind
f. double-blind
g. matched pairs (dependent samples)
h. block design
i. independent samples
j. explanatory variable (What is it?)
k. response variable (What is it?)