Week 7 - Assignments

Question 3

Several factors influence the value obtained for a t statistic. Some factors affect the numerator of the t statistic and others influence the size of the estimated standard error in the denominator. For each of the following, indicate whether the factor influences the numerator or denominator of the t statistic and determine whether the effect would be to increase the value of t (farther from zero) or decrease the value of t (closer to zero). In each case, assume that all other factors remain constant.

1. Increase the variability of the scores.
2. Increase the number of scores in the sample.
3. Increase the difference between the sample mean and the population mean.

Question 5

What is the relationship between the value for degrees of freedom and the shape of the t distribution? What happens to the critical value of t for a particular alpha level when df increases in value?

Question 12

Last fall, a sample of n = 25 freshman was selected to participate in a new 4-hour training program designed to improve study skills. To evaluate the effectiveness of the new program, the sample was compared with the rest of the freshman class. All freshman must take the same English Language Skills course, and the mean score on the final exam for the entire freshman class was = 74. The students with the new program had a mean score of M = 78 with SS = 2400.

1. On the basis of these data, can the college conclude that the students in the new program performed significantly better than the rest of the freshman class? Use a one-tailed test with = .05.
2. Can the college conclude that the students in the new program are significantly different from the rest of the freshman class? Use a two-tailed test with = .05.

Question 14

The herbal supplement ginkgo biloba is advertised as producing an increase in physical strength and stamina. To test this claim, a sample of n =36 adults is obtained and each person is instructed to take the regular daily dose of the herb for a period of 30 days. At the end of the 30-day period, each person is tested on a standard treadmill task for which the average, age-adjusted score is = 55. The individuals in the sample produce a mean score of M = 58.5 with SS = 5040.

1. Are these data sufficient to conclude that the herb has a statistically significant effect using a two-tailed test with = .05?
2. What decision would be made if the researcher used a one-tailed test with = .05? (Assume that the herb is expected to increase scores.)

SPSS Assignment

The Oak Harbor School used the Dumbarton University Math Battery (DUMB) to test the math achievement of the two 6th-grade sections. The publisher of the test reports that the mean score for all students taking the DUMB test that year was 775. The principal is interested in finding out if the 6th-grade students in her school did better than the national mean, as a whole, and whether female students, by themselves, did better than the national mean.

Use the Oak Harbor 1.sav file (provided in the Doc Sharing area) which contains the results of the DUMB test in order to test whether the Oak Harbor students did better than the national average and whether the female students, as a group, did better than the national average.

• State the null and alternative hypotheses for testing the data set against the mean of 775.
• Conduct one sample t test at the .05 level.
• Copy or copy object and paste relevant output from the statistical test.
• State whether or not the null hypothesis is accepted or rejected based on the results of the statistical test. Use the conventions described by Gravetter and Wallnau on page 235 to present your report.
• In a brief paragraph (3–5 sentences), discuss your findings as though you were explaining it to the principal.

Price: $19.91

Solution: The downloadable solution consists of 8 pages, 1191 words and 4 charts.
Deliverable: Word Document