Question

Learning Objectives

1. Learn more about the statistical analysis tools in SPSS.
2. Practice manual calculations and confirm with SPSS output.
3. Walk through all steps of hypothesis testing for a related-samples t-Test.

About Your Data

A statistics student was late on completing the final statistics project. While racking her brain for ideas, she watched her cat eating supper and noticed how much quicker the cat ate the new brand of cat food. Feeling desperate about the project, she decided to figure out if cats really do prefer Brand A over Brand B. She catnapped six neighborhood cats (No judging!) and deprived them of food for 10 hours. Then she gave the cats Brand A, measured the amount of food eaten, deprived them of food for another 10 hours and gave them Brand B. The amounts eaten in grams are listed below:

Cat	Brand A	Brand B
1	32	33
2	40	30
3	36	32
4	37	29
5	37	30
6	36	25

Instructions

The steps below are slightly different from the ones laid out by your textbook author. I want you to follow my six steps below. Also, because it can be difficult and time consuming trying to figure out how to insert symbols into a word processing document, I would like you to complete your manual work with pencil and paper.

Six Steps of Hypo Testing and Manual Calculations

You will be conducting a related-samples t-Test (SPSS calls it a Paired-Samples test) to determine whether the cats have equal preference for Brands A and B. Your alpha level will be .05.

Write out your six steps for this ethically dubious though highly entertaining study. ;-)

1) State H₀ using symbols AND words
2) State H₁ using symbols AND words
3) State your alpha level
4) Articulate your rejection rule ("Reject H₀ if |obtained t| ≥ critical t, t_crit = _____")
5) Manually calculate your related-samples t value (Show your work. Carry your calculations out to two decimal places. Feel free to calculate standard deviation on calculator.)
6) State your conclusions in four parts. a. What did you do? b. What did you find? c. What does it mean? d. What can we do with these findings? (REFER BACK TO ABOVE VIDEO for explanation and examples of the different parts of Step 6. Follow the template provided in the video.)

Effect-Size Statistics

What are Cohen's d and the confidence interval of the difference? The confidence interval is listed in the SPSS output. You can do a quick internet search for "Cohen's d" calculator and find many websites that will allow you to quickly perform that calculation. Once you have your effect sizes, explain what they mean.

Decision-Making Errors

Of course, there is always the possibility of Type I or Type II error. Which type of error is relevant in this case? What are some possible consequences of this type of error?

Answer 1