Problem Set 6.1: One–Sample t Test

Criterion: Hand calculate a one-sample t test.

Data: Rex’s Flower Shop advertised freshly cut roses that last longer than other roses. The mean vase life for a rose is 8 days. The following is a sample of the vase life of 9 bouquets of roses from Rex’s Flower Shop: 8, 6, 12, 11, 8, 9, 14, 15, 10.

Instruction: Complete the following:

a. State the nondirectional hypothesis.

b. State the critical t for α = .05 (two tails).

c. Calculate t. Show your work.

d. Answer: Is the vase life of Rex’s roses significantly different than the population mean? Explain.

Problem Set 6.3: Confidence Intervals

Criterion: Calculate confidence intervals using SPSS.

Data: Use the SPSS output from Problem Set 6.2 above.

Instruction: Based on the SPSS output from Problem Set 6.2, including a test value (population mean) of 8, calculate the 95% confidence interval.

Problem Set 6.4: Standard Error of the Difference Between the Means

Criterion: Analyze the relationship between standard error and the difference between the means.

Data: A researcher examines the results of two separate studies. In the first study, the difference between Group A and Group B is two points, but the standard error is large and the difference is not significant. In the second study, the difference between Group A and Group B is also two points, but the standard error is small and the difference is significant.

Instruction: Answer this: What might be the reason for the difference in the standard error across the two studies?

Problem Set 6.6: Independent Samples t Test

Criterion: Identify IV, DV, and hypotheses and evaluate the null hypothesis for an independent samples t test.

Data: Use the information from Problem Set 6.5.

Instruction: Complete the following:

a. Identify the IV and DV in the study. 

b. State the null hypothesis and the directional (one-tailed) alternative hypothesis.

c. Can you reject the null hypothesis at α = .05? Explain why or why not.