Winter 2017 Some Lab Class exercises on Experimental/Correlational Research; Identifying IVs and DVs; Confounds and Threats to Internal Validity
I. Experimental/Correlational Studies
1. The limitations of nonexperimental research were brought to the attention of the public by the results of an experiment on the effects of postmenopausal hormone replacement therapy (part of the Women's Health Initiative). An experiment is called a clinical trial in medical research. In the clinical trial, participants were randomly assigned to receive either hormone replacement therapy or a placebo (no hormones). In 2002, the investigators concluded that women taking the hormone replacement therapy had a higher incidence of heart disease than did women in the placebo (no hormone) condition.
At that point, they stopped the experiment and informed both the participants and the public that they should talk to their physicians about the advisability of this therapy. This finding contrasted dramatically with the results of nonexperimental research in which the women taking hormones had a lower incidence of heart disease; in these earlier studies, researchers compared women who were already taking hormones with women not taking hormones. Why do you think the results were different between the experimental and nonexperimental research?
2. Each of the following describes the outcome of a correlational study. [May need to review diff between positive and negative correlation]. Describe at least two ways of interpreting each correlation: - There is a positive correlation between the level of dominance shown by mothers and the level of shyness shown by children. - There is a negative correlation between aerobic fitness level and depression. - There is a positive correlation between the number of books found in the home and the college GPAs of the students living in those homes. - Seating location in class is correlated with grades - the closer to the front, the higher the grade.
H. Identify the independent and dependent variables in the following descriptions of experiments:
1. Students watched cartoons either alone or with others and then rated how funny they found the cartoon to be
4. Workers at a company were assigned to one of two conditions: one group completed a stress management training program, another group of workers did not participate in the training. The number of sick days taken by these workers was examined for the two subsequent months.
5. Participants read a handout about a company executive and looked at a photograph of her. From a list of 25 adjectives, participants circled those that seemed to apply to the executive. A participant's score was the number of positive adjectives circled. For half of the participants the executive was smiling; for the other half the expression was neutral.
III. Confounds and Threats to Internal Validity
1. The following research design has a potential threat to the internal validity of the research. Indicate the confound, and how it might be eliminated. The Pepsi-Cola company conducted the "Pepsi Challenge" by randomly assigning individuals to taste either a Pepsi or a Coke. The researchers labeled the glasses with only an "M" (Pepsi) or "Q" (Coke) and asked the participants to indicate which they preferred. The research showed that subjects overwhelmingly preferred the "M" glass over the "Q" glass What cant the researchers conclude that Pepsi was preferred over Coke?
For each of the following, identify the independent and dependent variables, and at least one extraneous variable that has not been controlled (i.e., that is creating a confound).
2. A testing company is trying to determine if a new type of golf club (club 1) will drive a golf ball greater distances than three competing brands (clubs 2-4). Twenty male golf pros are recruited to participate Each golfer hits 50 balls with club 1, then 50 more with club 2, then 50 with club 3, and then 50 with club 4. To add realism, the experiment takes place over the first 4 holes of an actual golf course - the first set of 50 balls is hit from the first tee, the second 50 from the second tee, and so on. The first four holes are all 380-400 yards in length.
3. You are interested in the ability of schizophrenic patients to judge different time durations. You hypothesize that loud noise will adversely affect then judgments. Participants are tested in two ways. In the "quiet" condition, half of the patients are tested in a small soundproof room. The other half in the "noisy" condition are tested in a nurse's office where a stereo is playing music at a loud volume. Because of scheduling difficulties, locked-ward patients are available for testing only on Monday and open-ward patients are available for testing only on Thursday. Furthermore, the soundproof room is only available on Monday.
For each of the following examples, identify which of the following threats to internal validity is most likely to provide a reasonable alternative account of the results. History Testing Statistical Regression Maturation Mortality Selection Selection X History Selection X Mortality
4. A college dean is upset about the so-called attrition rate - the percentage of freshman who return to college as sophomores. Historically, the rate has been around 75%, but in the academic year just begun, only 60% of last year's freshman return. The dean puts a tutoring program into effect and then claims credit for its effectiveness when the following year's attrition rate is 71%.
5. Twelve women who ask to be considered for a home birthing program are compared with a random sample of other pregnant women who undergo normal hospital procedures for childbirth. Women in the first group spend an average of 6 hours in labor, while those in the control group spend an average of 9 hours in labor.
6. A company decides to introduce a flextime program. It measures productivity for January. runs the program for 6 months, and then evaluates productivity during the month of June. Productivity rises.
7. The following experiment is modified from Triplett (1898) who published the first social psychology experiment on competition. Read the description and answer the following questions.
Ten-year-old children reeled line onto a fishing reel. Thirty children were tested individually before school using brand-new reels. They were told to "reel as fast as you can.' Thirty other children were tested after school with the same reels. They were divided into groups of three and told to "be the fastest in your group." The students who competed against others reeled in an average of 65 feet of line. Those who reeled individually averaged 50 feet of line.
The conclusion was that competition improves performance. - Identify features of this experiment that cause problems for internal validity (i.e., identify confounds). - Identify aspects of the experiment that could lead to questions about external validity. - Identify one control variable that is the same for both groups.
Articles :
Depth of Processing and the Retention of Words in Episodic Memory
(Fergus I. M. Craik and Endel Tulving)
A Lack of Self-Consciousness in Autism
Self-memory biases in explicit and incidental encoding of trait adjectives
(David J. Turk *, Sheila J. Cunningham, C. Neil Macrae)