Question

A different researcher is interested that caffeine will affect the speed with which people read but design a study with four conditions -- a placebo group (a group that gets a pill that looks like the caffeine group does, but it does not contain caffeine), a no-drug condition, a 50mg caffeine condition, and a 100mg caffeine condition. The researcher randomly assigns 16 people into one of the four groups. An hour after the treatment, the 16 participants in the study are asked to read from a book for 1 minute; the researcher counts the number of words each participant finished reading. The following are the data for each group:

100mg Caffeine (Group 1)

500 550 500 450

50mg Caffeine (Group 2)

450 400 500 450

No Caffeine (Group 3)

400 410 430 440

Placebo (Group 4)

400 410 430 440

Answer the following questions using the Analysis of Variance instead of the t-test

a. What is the research hypothesis?

b. What is the null hypothesis?

c. What is dfbetween and dfwithin? What is the total df for this problem?

d. What is SSbetween and SSwithin? What is the total SS for this problem?

e. What is MSbetween and MSwithin?

f. Calculate F.

Use an a-level of .05 to answer the questions below

g. Draw a picture of the F distribution for dfbetween and dfwithin above, and locate F on the x-axis.

h. What is the critical value of F, given dfbetween and dfwithin? Indicate the critical value of F (and its value) in your drawing. Also indicate what the area is in the tail beyond the critical value of F.

i. Can you reject the null hypothesis?

j. Can you accept the research hypothesis?

Answer 1