SFL 290 assignment #2

Assignment #2
Joy Prior
Research Methods SFL 290
Experimental Design
1. Dr. Duncan was interested in studying the effects of taking a marriage enrichment course on marital satisfaction. At the beginning and end of the semester, the researcher distributed a questionnaire regarding marital satisfaction to students who had taken the course. Because on the average students improved their marital satisfaction scores after taking the course, he felt he had succeeded.
a) the type of experimental design (please also diagram with appropriate notation)
quasi-experimental nonequivalent control group design
Step 1 Step 2 Step 3 Step 4
Participants are in the marriage enrichment course on marital satisfaction A pretest is administered (questionnaire regarding marital satisfaction to students) A treatment is administered (the class courses) A posttest is administered (questionnaire regarding marital satisfaction to students)
b) the independent variable: course on marriage enrichment and the dependent variable: marital satisfaction
c) Possible confounding variables (threats to internal validity): if simply because a couple is taking the class together they spend more time together because they are walking to class, sitting in class, studying for class, and discussing class and simply spending more time together causes their marital satisfaction to increase not the actual teacher.
d) How to "unconfound" the experiment (redesign the experiment using a classical experimental design) randomly assign participants to the marriage course and randomly assign a control group to take the pretest and posttest but to not participate in the marriage course but another course with similar time commitment.

2. A family therapist was interested in testing out a new “brief therapy” program that she had developed for use with individuals. She went to the alternative high school and asked for volunteers to participate in her “brief therapy” program, and 15 people volunteered. She used brief therapy with these volunteers and then assessed them using a personal adjustment questionnaire. She found that on the average the participants scored fairly high on the adjustment measure, so she deemed her brief therapy program as successful.
a) the type of experimental design (please also diagram with appropriate notation)
one-shot case study design
Step 1 Step 2 Step 3
Participants volunteer to participate in her “brief therapy” program She used brief therapy with these volunteers assessed them using a personal adjustment questionnaire
b) the independent variable: the treatment or brief therapy program received and the dependent variable: the scores on the adjustment questionnaire
c) Possible confounding variables (threats to internal validity) the students who agreed to participate are all a friends and after joining her brief therapy program they all realized that they needed help badly. So together they signed up for a support group and have been receiving in depth attention and therapy from the support group they all joined.
d) How to "unconfound" the experiment (redesign the experiment using a classical experimental design) she would have to randomly select the participants for the experiment and then randomly assign some participates to the brief therapy program and some participates to not participate in the program.

3. Mr. I. M. A. Mapp wanted to test a new “sing-a-long” method to teach geography to eighth graders (e.g. students sing the names of the countries in Africa to a well-known tune). First, he assessed the students’ knowledge of African geography, and then he used the sing-a-long method in his first period class and traditional methods with his second period class. At the end of the term, Mr. Mapp found that the first period class scored significantly higher than the second period class on the African geography test. He concluded that the sing-a-long method was a total success.
a) the type of experimental design (please also diagram with appropriate notation)
pretest posttest control group design
Step 1 Step 2 Step 3 Step 4
Participants are assigned according to class period Pre-test he assessed the students’ knowledge of African geography he used the sing-a-long method Post-test he assessed the students’ knowledge of African geography
Participants are assigned according to class period Pre-test he assessed the students’ knowledge of African geography traditional methods with his second period class Post-test he assessed the students’ knowledge of African geography
b) the independent variable: teaching method (traditional/sing-a-long) and the dependent variable: students’ knowledge of African geography measured by a test
c) Possible confounding variables (threats to internal validity) because of campus scheduling anyone involved in a school sport has weight training for first period and the majority of the students in Mr. Mapp’s second period class are involved in school sports. These students all arrive to class tired from working out, and have little time to study because after school they are at practice.
d) How to "unconfound" the experiment (redesign the experiment using a classical experimental design) Give the student’s the pretest and post-test and then instead of comparing the scores directly compare the improvements in the scores.

4. Dr. Robinson was interested in studying the effect of taking a course in parenting upon attitudes toward childrearing. At the end of the semester, he distributed a questionnaire to students who had taken the course. Questionnaires were also given to an equal number of students who had not taken the course. Students who had taken the course had different attitudes from the students who had not taken the course (ie they had more positive attitudes about having large families).
a) the type of experimental design (please also diagram with appropriate notation)
quasi-experimental static group comparison design
Step 1 Step 2 Step 3
Participants volunteer to participate in the course Participants take the course in parenting and childrearing distributed a questionnaire to students who had taken the course
Participants Participants are unaware of study or the current course in parenting and childrearing and do not take course distributed a questionnaire to students who have not taken the course
b) the independent variable: taking a course on parenting and child rearing and the dependent variable: attitude towards families ie having large families; measured with a questionnaire
c) Possible confounding variables (threats to internal validity) the students who are taking the parenting and childrearing course signed up for the class while the students who are not taking the course did not sign up for the course for one reason or another. The students who did sign up for the course obviously show a level of interest in parent and child rearing because they signed up for the course and probably already had a more positive attitude about families than the students who did not sign up for the course.
d) How to "unconfound" the experiment (redesign the experiment using a classical experimental design) give all of the students a pretest and then randomly assign them to either take the course or not to take the course, which would weaken the effect of the convenience sampling.

5. A high school introduced a critical thinking English program in all of the eleventh grade classes. At the end of the school year, all eleventh grade students took the Scholastic Aptitude test (SAT). The school reported that the SAT verbal scores of the students having the new critical thinking program were significantly higher than the scores of the previous eleventh grade class. The school attributed the difference to the critical thinking program.
a) the type of experimental design (please also diagram with appropriate notation)
static group comparison design
Step 1 Step 2 Step 3
Participants from current school year of eleventh grade class in particular high school introduced a critical thinking English program students took the Scholastic Aptitude test (SAT)
Participants from previous school year of eleventh grade class in particular high school No critical thinking English program students took the Scholastic Aptitude test (SAT)
b) the independent variable: critical thinking English program and the dependent variable: scores on Scholastic Aptitude test (SAT)
c) Possible confounding variables (threats to internal validity) in the previous school year there were different teachers but because of the low scores all of the teachers got fired and new teachers were hired on the same year that the new program was introduced.
d) How to "unconfound" the experiment (redesign the experiment using a classical experimental design) the students could be randomly assigned to either participate in a class that used the critical thinking English program or to participate in a classroom that was not going to use the critical thinking English program and then given a pretest to determine what their original SAT score without treatment or time would be. At the end of the year administer the SAT again and compare the improvement in scores.

6. Dr. Harper wanted to test a new counseling method (cognitive behavioral therapy) with his clients who were experiencing clinical depression. He used cognitive behavioral therapy with his morning clients and his regular form of counseling with his afternoon clients. At the completion of therapy, Dr. Harper found that those who had completed cognitive behavioral therapy were significantly less depressed than those who had experienced his traditional approach.
a) the type of experimental design (please also diagram with appropriate notation)
static group comparison design? Or poorly designed posttest-only control group design because not random
Step 1 Step 2 Step 3
Participants are assigned to group by the time of day that they come into the office cognitive behavioral therapy Measure of level of depression
Participants are assigned to group by the time of day that they come into the office regular form of counseling Measure of level of depression
b) the independent variable: cognitive behavioral therapy and the dependent variable: measure of level of depression
c) Possible confounding variables (threats to internal validity) the afternoon clients are all members of the mental hospital and Dr. Harper counsels them for free as a service to the community; they are clinically classified as more depressed than the morning clients who are middle aged mothers and fathers who pay Dr. Harper for his services.
d) How to "unconfound" the experiment (redesign the experiment using a classical experimental design) when a client enters his office for an appointment Dr. Harper flips a coin. If the coin is heads he uses cognitive behavioral therapy with that client, but if the coin is tales he uses his regular form of counseling.

Mean, Median, and Mode Calculations
Sample 1: 71, 76, 74, 78, 77, 72, 73, 75, 75, 79 Mean: 75 Median: 75 Mode: 75 .
Total: 750
N: 10
71, 72, 73, 74, 75, 75, 76, 77, 78, 79
Sample 2: 71, 76, 74, 78, 77, 72, 73, 75, 75, 99 Mean: 77 Median: 75 Mode: 75 .
Total: 770
N: 10
71, 72, 73, 74, 75, 75, 76, 77, 78, 99
Sample 3: 71, 76, 74, 78, 77, 72, 73, 75, 75, 19 Mean: 69 Median: 74.5 Mode: 75 .
Total: 690
N: 10
19, 71, 72, 73, 74, 75, 75, 76, 77, 78
*Note the underlined scores are atypical outliers in samples 2 and 3. Will they “skew” the mean? ___yes____