Consider a study testing the hypothesis that on average individuals who take a new cognitive enhancement drug will remember more words in a recall memory test than those in the population. Given the information provided, the Cohen's d value is:
Mean of population 7 words
Population standard deviation 2
Sample size 5
Data for the 5 participants 10 words, 7 words, 11 words, 11 words, & 11 words

a. 3.37.
b. 1.50
c. -3.37.
d. - 1.50.