Question

For each of the studies, please indicate the following:

1) Independent variable(s)

2) Number of IVs

3) The levels the independent variable(s)

4) Dependent variable

(for correlation, list all variables here)

5) Between (B/S) or within-subjects (W/S)?

6) What type of design is being used?

7) What is the appropriate statistic?

*If a question isn’t applicable to a particular design, please note that as well

Study1: A team of cognitive psychologists conducted a study on the effects of sleep deprivation on short-term memory decay. Forty-eight participants stayed in a lab for two days. Twenty-four of the participants are randomly assigned to a condition in which they are not permitted to sleep during that period. The other twenty-four are allowed to sleep whenever they want. At the end of the two days, the participants complete a task that involves reading a list of 20 words, then recalling as many words as possible.

Study2: A researcher examined the effect of different kinds of music on general math ability. Forty-eight participants were randomly assigned to do a series of math tasks under one of three conditions: 16 while listening to soft gentle music, 16 while listening to loud intense music, and 16 while in silence. The math quiz contained arithmetic, geometry, and word problems. There were 25 items that were 2 points each.

Study3: A health psychologist conducted a study on the how the number of hours a person exercised each week relates to the number of days being sick per year. Participants were randomly selected from the community and provided self-reports through a series of questions on the topics of interest.

Study4: A study was designed to test the effects of science fiction movies on participants' belief in the supernatural. A scale was designed to measure the degree that a participant believes in the supernatural on a 1-7 Likert Scale (high scores indicate high levels of belief). Fifty-seven participants, selected via random digit dialing (RDD) responded to the scale before and after watching Return of the Jedi, a popular science fiction movie.

Study5: A researcher at a drug treatment center wanted to determine the best combination of treatments that would lead to more substance free days. This researcher believed there were two key factors in helping drug addiction: type of treatment and type of counseling. The researcher was interested in either residential or outpatient treatment programs and either cognitive-behavioral, psychodynamic, or client-centered counseling approaches. As new clients enrolled at the center they were randomly assigned to one of six experimental groups. After 3 months of treatment, each client’s symptoms were measured.

Study6: An organizational psychologist is hired as a consultant by a person planning to open a coffee house for college students. The coffee house owner wants to know if her customers will drink more coffee depending on the ambience of the coffee house. To test this, the psychologist sets up three similar rooms, each with its own theme (Tropical; Old Library; or New York Café ) then arranges to have thirty students spend an afternoon in each room while being allowed to drink all the coffee they like. (The order in which they sit in the rooms is counterbalanced.) The amount each participant drinks is recorded for each of the three themes.

Study7: A manager at a retail store in the mall wants to increase profit. The manager wants to see if the store’s layout (one main circular path vs. a grid system of paths) influences how much money is spent depending on whether there is a sale. The belief is that when there is a sale customers like a grid layout, while customers prefer a circular layout when there is no sale. Over two days the manager alternates the store layout, and has the same group of customers come each day. Based on random assignment, half of the customers are told there is a sale (20 % will be taken off the final purchases), while the other half is told there is no sale. At the end of each day, the manager calculates the profit.

Answer 1

Study 1:

1) Independent variable: Binary(weather person slept for 2 days or not)

2) Number of independent variable: 1 variable having 42 obs

3) There are no levels applicable in the study

4) Depended variable: Number of words recalled by each individual.

5) As sleep cycle/requirement for each individual is diffferent; not depended on each other, correlation will be 0. the only correlation that exists will be if the person slept and the no. of words he recalled.

6) Equality of means from 2 populations can tell us if avg words recalled by sleep deprived individuals differ significantly from averagew words recalled by those getting adequate sleep, hence giving the effects of sleep deprivation on short-term memory decay.

7) Welch test will be the best.

Study 2:

1,2) There will be 2 independent variables: first will be binary if music was soft or not. other will be if music was loud or not. the thirst condtion of being silent will not be a separate independent variable as those not satisfying first 2 cases will automatically be assigned in 3rd case.(to avoid dummy variable trap).

3) If we consider 2 independent variables, there will be no levels. but if we consider only 1 variable: type of music then there will be 3 levels, soft, loud, silent.

4) Dependent variable: Score obtained in math quiz.

5) there will be correlation of type of music on score in quiz; no within sample correlation will be observed.

6) Equality of means from 3 populations can tell us how music impacts math solving ability. ( If the section of maths: arithmetic, geometry, and word problems are taken separately and their seaprate scores are evaluated then Randomised block Design model can be used)

7) Likelihood ratio test will give appropriate test statistic.

study 3:

1,2,3) independent variable:  No. of hours the person exercised in a week. (no levels)

4) dependent variable: No. of days in year he is sick.

5) there will be correlation between the days he excercised and days he fell sick. (data will have to be standardized.)

6,7) Direct regression will show how the number of hours a person exercised each week relates to the number of days being sick per year.

Study 4)

1) Independent variable1: the degree that a participant believes in the supernatural on a 1-7 Likert Scale before watching the movie.

Independent variable2: the degree that a participant believes in the supernatural on a 1-7 Likert Scale after watching the movie.

2) No. of independent variables: 2

3) Levels : 7 (high scores indicate high levels of belief).

4) Dependent variable: Binary (was the belief due to movie or not)

5) there will be between sample correlation as the same person's resonse is considered in 2nd variable as well. but there will be no relation between one person and other person.

6,7) Paired t test used. test statistic:  
m and s are the mean and the standard deviation of the difference (d), respectively. Follows t distribution with n-1 d.f

(here n=57)