Question

1. A researcher wants to examine how the chemical tryptophan, contained in foods such as turkey, can affect mental alertness, at an alpha of .05, two tailed.
   A sample of n = 25 college students is obtained and each student’s performance on a familiar video game is measured before and after eating a traditional Thanksgiving dinner including roast turkey.
   After the meal, The average decrease in scores was M = 8 points, with variance s² = 225 for the difference scores. Answer the questions below (6 points total this problem).
   1. What are the df?

2. What is the Standard error?

3. What is the calculated value of T?

4. Assume the critical cutoff for a two tailed T is plus or minus 2.35. Is your finding significant or not? Say something about why you can or cannot reject the null

5. Compute r² to measure the size of the effect.

6. Write a sentence demonstrating how the outcome of the test and the measure of effect size would appear in a research report.

Answer 1

There is sufficient evidence that chemical tryptophan, contained in foods such as turkey, affects mental alertness significantly. However r²=0.0664 indicates small effect size.