A study was conducted to assess whether red bull enhanced the exam performance of first year under-graduate students; the effects of red bull were tested on students that were exposed to either a multiple choice exam or an unseen essay. The researchers tested a total of 80 participants, with 20 assigned to each of four experimental groups resulting from a factorial combination of the two independent variables. The effects of red bull were assessed on two dependent measures; mean mark obtained in each one of the four experimental conditions and time taken to complete each type of examination in minutes. To analyze the results, for each dependent measure the researcher used a two-factor ANOVA each with two levels:  type of exam (multiple choices vs. unseen exam); drug condition (placebo vs. red bull).

Table: Mean mark

Table: Time taken in minutes to complete examination

a. Type of examination produced significant main effects on both mean mark and time taken to complete the examination. Referring to the table of means, how would you describe verbally the effects of type of examination on the two dependent measures used in this study?

b. Did red bull produce significant main effects on both mean mark and time taken to complete the examination? Use the table above of means to support your answer?

c. The 'interaction effect' for the dependent variable mean mark was significant. Using the table of means, write a statement describing how Red bull appears to affect the mean mark received in the unseen examination.

d. Another researcher wishing to replicate these results considered using a repeated measures design for the type of examination factor, to reduce the number of participants that had to be recruited. Briefly explain what a repeated-measures design is and how would it be implemented here. What further advantage would this provide here?