Question: Based on previous research and sound theoretical considerations, an experimental psychologist believes that memory for pictures is superior to memory for words. To test this hypothesis, the psychologist performs an experiment in which students from an introductory psychology class are used as subjects. Eight randomly selected students view 30 slides with nouns printed on them, and another group of eight randomly selected students views 30 slides with pictures of the same nouns. Each slide contains either one noun or one picture and is viewed for four seconds. After viewing the slides, subjects are given a recall test, and the number of correctly remembered items is measure. The data are shown here:

No. of pictures Recalled No. of nouns recalled

18 12

21 9

14 21

25 17

23 16

19 10

26 19

15 22

a. What is the alternative hypothesis?

b. What is the null hypothesis?

c. What is the value of t obtained.

d. What is the value of t-crit.

e. What might you conclude using α = 0.05 ₂ tail?

e. What type error might have been made?

f. Estimate the size of the real effect using omega squared and cohen’s d. Is the effect a large one?