What are the advantages and disadvantages in the use of a posttest-only control group design versus a pretest-posttest control group design?

QUIZ501 25 QUESTIONS

1. A researcher is interested in whether students who attend private elementary schools do any better on s standard test of intelligence than the general population of elementary school children. A random sample of 75 students at a private elementary school is tested and has a mean intelligence test score of 103.5. The average for the general population of elementary school children is 100 (σ = 15).

a) Is this a one- or a two- tailed tests?

b) What are Ho and Ha for this study?

c) Compute zobt

d) What is zcv?

e) Should Ho be rejected? What should the researcher conclude?

f) Calculate the 95% confidence interval for the population mean, based on the sample mean.

2. Assume that the average person in America weights 150 pounds (μ). You want to determine whether colleges students weigh less than the average America, Following are the wights collected on a sample of colleges students: 120, 105, 166, 170, 145, 149, 135, 115, 168, 138.

a) Is this a one- or two-tailed test?

b) What are Ho and Ha for this study?

c) Compute tobt

d) What is tcv?

e) Should Ho be rejected? What should the researcher conclude?

3. How does a t test differ from a z test in terms of when it is used, how it is calculated, and how we determine significance?

4. According to the U.S. Bureau of the Census, 75% of adults regularly drank alcohol in 1985. An investigator predicts that fewer adults drink now than drank then. A sample of 100 adults is asked about their current drinking habits; 67 report drinking, and 33 report not drinking.

a) What is X2obt?

b) What is (are) the df for this test?

c) What is X2cv?

d) What conclusion should be drawn from these results?

5. A health magazine recently reported a study in which researchers claimed that iron supplements increased memory and problem-solving abilities in a random sample of college women. All of the women took memory and problem-solving tests at the beginning of the study, then took iron supplements, and then took the same tests again at the end of the study. What is wrong with this design? What confounds could be leading to the results of improved memory and problem-solving skills?

6. In an experimental study of the effects of exercise on stress, participants are randomly assigned to either the no exercise or the exercise conditions. Identify what type of study this is—between-, within-, or matched-participants. In addition, identify the independent and dependent variables and the control and experimental groups.

7. What are the advantages and disadvantages in the use of a posttest-only control group design versus a pretest-posttest control group design?

8. What is a confound and how is it related to interval validity?

9. What is the relationship between external validity and the college sophomore problem?

10. Explain what counterbalancing is, how it is achieved, and which confound it helps to minimize.

11. Explain what a Latin square is and how it helps with counterbalancing.

12. According to some research, males have better spatial skills than do females; and according to other research, females have better reading skills than males. A student is interested in determining which sex performs better on a word-search puzzle (a puzzle in which the words are hidden vertically, horizontally, and diagonally within an array of letters) since this type of puzzle involves both spatial and reading skills. A sample of males and females volunteer to participate and are given 10 minutes to work on a 50-word puzzle. The number of words correctly recognized is recorded for each subject, and the resulting data are as follows:

Males Females

12 15

8 12

9 11

11 18

10 13

12 14

7 17

The paper must be neatly formatted, double-spaced with a one-inch margin on the top, bottom, and sides of each page. When submitting hard copy, be sure to use white paper and print out using dark ink. If it is hard to read your essay, it will also be hard to follow your argument.