The method used

Name the method used in the studies described below:
A) Researchers are interested in influences on self-esteem. Participants are given a set of anagram problems to solve in a five-minute period. Half are randomly assigned to receive very easy anagrams and half are given difficult ones. After completing as many of the anagrams as they can, participants are given a questionnaire labeled “Thoughts and Feelings Questionnaire” that is really a measure of self-esteem.
● a) Observational
● b) Correlational
● c) Experimental
B) A researcher is interested in the relationship between caffeine consumption and level of stress. She has participants keep a diary for one week, during which they count the number of cups of coffee and tea, energy drinks, and cola-based soft drinks they consume, as well as record their consumption of chocolate and medications that have caffeine as an ingredient. In addition, participants complete a measure of “daily hassles” experienced during the week.
● a) Observational
● b) Correlational
● c) Experimental
C) A pair of psychologists are interested in the effects of mood on helping. They give some random people free tickets to a happy movie. They then have a confederate drop papers in front of the people who just got out of the movie and people who are only walking by and have not just seen a happy movie for free. The researchers watch to see if the participants help pick up the dropped papers.
● a) Observational
● b) Correlational
● c) Experimental
D) Dr. Young examines how males portray themselves on dating apps. She systematically reviews profile pictures of men on Tinder and notes if they tend to post pictures of just themselves alone or with a group of friends.
● a) Observational
● b) Correlational
● c) Experimental