Assignment - Experimental, quasi-experimental, and ex post facto designs

1. A researcher wants to investigate whether college students' knowledge of the negative consequences of the overuse of credit will affect their attitudes about credit use. He plans to recruit one family studies class of 30 students from a local college campus (already enrolled in one class) and measure their attitudes toward credit with an attitude scale. Then, on four successive days, the researcher will teach them four lessons on the consequences of the overuse of credit: wage garnishment, repossession, foreclosure, and bankruptcy. On the fifth day, the researcher will administer an alternate form of the credit attitude scale (one intended to measure the same attitude). Then, he will try to infer whether college students' knowledge of the negative consequences of the overuse of credit affects their attitudes about credit use.

a. What is the independent variable and what is the treatment that the researcher will use to manipulate that variable?

b. What is the dependent variable in this study?

c. What type of research design is this researcher planning to use? Diagram it.

Predictive research

G1      O1   X     O2

d. State the most likely alternative hypothesis of this researcher.

e. What are the most important threats to the internal validity of the study? (Give an example of each threat in the language of the research problem.)
- History: researchers plan to measure students' attitudes toward credit with an attitude scale on four successive days, by teaching them four lessons on the consequences of the overuse of credit and then on the fifth day, the researcher will administer an alternate form of the credit attitude scale (one intended to measure the same attitude).
- Maturation: students will get more experienced, wiser and more knowledgeable about the negative consequences of the credit's overuse.
f. What two threats to internal validity are involved in this researcher's plan to use an alternate form of the credit attitude scale? What is the trade-off?
- Instrumentation: after the researcher administer an alternate form of the credit attitude scale, he will try to infer whether college students' knowledge of the negative consequences of the overuse of credit affects their attitudes about credit use. This might be due to the change in the measuring instrument between on the fifth day.
- Testing: the researcher will administer an alternate form of the credit attitude scale (one intended to measure the same attitude).
- What is the trade-off? As more knowledgeable, the college student get about the negative consequences of credit overuse, their attitudes about credit use will decrease.

g. Briefly describe the analysis this researcher would use to answer his research question (i.e., what would he compare to what?)
- If the researcher administer to the college student another alternate form of the credit attitude scale, then what would be different on the students' attitudes about credit use?

Suppose that instead of the design described, the researcher randomly assigned each of the 30 students to two groups. Suppose he did everything the same as before, except a teacher took one group of students on a field trip each of the four "treatment" days during their family studies class to a local historical site.

2 group G1

              G2

h. What type of research design is he now using? Diagram it.

 Two groups experimental design

i. Does this design now have a classic "placebo" control group?

 Yes, one group was randomly assigned to a different treatment group. The placebo group who will takes part in the test so as to compare the result with the group who do.

j. Compare and contrast these two research designs' internal and external validity.

 Using randomization to achieve internal and external validity in a research design, the statistical analysis has to be appropriate to the types of data collected, and the questions the researcher is trying to answer. Single group always have high internal validity because subjects works at their own controls, but should be extremely low compared to external validity of the other group. The placebo group study acquire external validity probably through the process of replication and extension for example, repeating the study in a different setting, with a different subject.

1. A research team wants to study the effect of handbag advertising on women's choice of handbags. They are concerned about the potential effects of the women having any clue before the ads are shown about the content of the study (particularly the treatment). They randomly assign 100 women (19-22 years old) to four groups. They ask two groups of women to choose a handbag from a group of four handbags before the treatment. Two other groups will not be asked initially about their handbag choices. Of the first two groups, one group will be shown a television program containing 40-second handbag ads on one of the handbags and the other group will be shown the program without ads. Of the last two groups, one group will see the program with the ads and the other group without the ads. Then, each woman will be asked to choose a handbag from a set of four possible handbags (including the one in the ads). Then, the researchers will try to infer whether women shown the handbag advertisements choose different handbags from the women not shown the ads (i.e., whether advertising affects women's choice of handbags).

a. What is the substantive independent variable in this study?

The four handbags before the treatment

Substantive variable: An element of theoretical interest within the experiment. The researcher plans to determine whether different values of the substantive variable produce different responses.

b. What additional (methodological) independent variable is planned?

Handbag advertisement

c. What is the dependent variable in this study?
Women's choice of handbags

d. What research design is this research team planning? Diagram it.
Experimental research design

e. What are the threats to internal validity of this research design?
Interaction of selection instrumentation

f. What is the third (methodological) null hypothesis in this study?
H0: Handbag advertisement do not show a significant effect on women's choice on handbags

g. (extra credit) Briefly explain how this team would analyze their data to answer their research question and deal with their methodological concern, including the two different possibilities that could occur in the test of the third null hypothesis.

2. A researcher wants to investigate whether college students' knowledge of the negative consequences of the overuse of credit will affect their attitudes about credit use. He plans to recruit two professors to help him in his research. One professor of family and consumer sciences is planning a unit of four lessons of credit, such as wage garnishment, repossession, foreclosure, and bankruptcy. The other professor in social studies is teaching a unit about Australia. Each professor' class has 30 students. At the beginning of the study, the researcher will measure each student's attitudes toward credit with an attitude scale. Then, each professor will teach her lessons. After that, the researcher will administer an alternate form of the credit attitude scale to each student. Then, he will try to infer whether college students' knowledge of the negative consequences of the overuse of credit affects their attitudes toward credit use.

a. What type of research design is this researcher planning to use? Diagram it.

b. What do you believe is the one most important threat to the internal validity of this study? (Use the specific languages of the problem.)

c. What could this researcher do to address this threat?

d. Compare and contrast this design to a previous research design (question #1: h). Which do you believe is the better research design? Why?

3. A researcher wants to investigate whether college students' knowledge of the negative consequences of the overuse of credit will affect their attitudes about credit use. The researcher will select a random sample of 100 college students from a list of all college students at CSUN. He will measure each student's knowledge of the negative consequences (delinquency, wage garnishment, foreclosure, bankruptcy, etc) of the overuse of credit with a 20-item self-report objective test. At the same time, he will measure each student's attitudes toward credit with an attitude scale. Then, he will try to infer whether college students' knowledge of the negative consequences of the overuse of credit affects their attitudes toward credit use. (He wants to infer cause-and-effect relationship.)

a. What type of research design is this researcher planning to use (be precise)? Diagram it.

b. Describe its advantage over other ex post facto designs.

c. Is history a threat to the internal validity of this design? Why or why not?

d. Is maturation a threat to the internal validity of this design? Why or why not?

e. It testing a threat to the internal validity of this design? Why or why not?

f. Is instrumentation a threat to the internal validity of this design? Why or why not?

g. Is mortality a threat to the internal validity of this design? Why or why not?

h. What is the most important threat to the internal validity of this study? What could this researcher do to address this threat? What could this researcher do to address this threat? Be specific in discussing this in relation to THIS particular study.

i. Describe another important threat to the internal validity of this design that is NOT a threat to any previous design we have considered.

j. Compare and contrast this research design to the research designs in question #1 (note: there are two designs in question #1: c & h) and question #3 in terms of both internal and external validity. Please be organized in this answer.

k. Which of these four designs do you believe is the best research design? Why?

Un grupo de monjitas ha pasando por delante de San Pedro para entrar al cielo. Entonces, San Pedro le pregunta a la primera:
- "Hermana Verónica, ¿ha tocado usted un miembro masculino alguna vez?"
- "Sí" -le contesta Verónica- "pero sólo con un dedito".
- "Pues hermana, lávese el dedo aquí en el agua bendita y luego entra".
A la segunda monja le hace la misma pregunta y ella le responde:
- "Sí, pero sólo con la mano".
- "Entonces, Hermana Camila, lávese la mano en el agua bendita y entre".
De pronto, llega corriendo y empujando la hermana Betsabé y se coloca al frente de la fila. San Pedro le pregunta:
- "¿Por qué tantas prisas, hija mía?"
- Y le contesta sor Betsabé... "Porque si tengo que hacer gárgaras con el agua bendita, quiero hacerlo antes de que la hermana Sonia meta el trasero."