On the basis of previous research and sound theoretical considerations, a cognitive 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 4 seconds. After viewing the slides, subjects are given a recall test, and the number of  correctly remembered items is measured. The data follow:

  

     

  

a. What is the alternative hypothesis? Assume that a directional hypothesis is warranted.

  

b. What is the null hypothesis? 

  

c. Using  what is your conclusion?

  

d. Estimate the size of the real effect.
 

No. of Pictures Recalled 18 21 14 25 23 19 26 15 No. of Nouns Recalled 12 9 21 17 16 10 19 22