Assignment #2 – t tests

The data that will be used in this assignment has been selected from a real dataset. It is the same dataset you used for Assignment #1 except that only individuals who are between the ages of 18 and 30 are included in the dataset. The scale is called the "Subjective Age Identity Scale" or SAIS. This scale assesses how old individuals feel on seven different dimensions (i.e., how old one feels mentally). These seven items can be averaged into a total score (SAIS_Total). The participants that completed this scale were selected from the general community.

For this assignment you will need to use the appropriate t-tests in SPSS to answer the following research questions. Each of these items are assumed to be measured at an interval level.

• Question 1: Do men and women differ on how old they feel physically (SAIS1)?
• Question2: Do men and women differ on their ideal age (SAIS7)?
• Question 3: Is there a difference between how old one feels physically (SAIS1) and how old one feels mentally (SAIS2)?

1. What type of t-test will you need to use to answer each of these questions and why? (3 marks)
2. What are the null and alternative hypotheses for each question? Write out in symbols and in words (3 marks)
3. That assumptions are required for this/these statistical test(s)? (3 marks)
4. Which of these assumptions can you test in SPSS? Test these assumptions. Does your data meet these assumptions? Why or why not? Does your data have any outliers? (5 marks)
5. Why are we concerned about violating assumptions (1 mark)
6. Run the appropriate t-tests in SPSS. Report your results using APA style (remember to include the effect size and its interpretation) (10 marks).
7. Calculate (by hand) the effect sizes for your analyses and be sure to include it in the report of your results above (2 marks). You may calculate either Cohen’s d or r ² as your effect size measure.
8. Explain the difference between statistical significance and practical significance. Which is more important and why (3 marks).

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