A psychology student carries out a test on short-term memory. She shows 20 commonly used words to ten 18-year-old males. As soon as the 20 words have been shown, the psychologist asks the participants to write down as many words as they can remember in five minutes. The sample of 18-year-old males can be seen as representative of the population of 18-year-old males.

The number of words correctly remembered by the participants are:

15, 7, 12, 14, 11, 10,4, 13, 9, 2

The median number of words remembered by 65-year-old males in this test is four. Carry out a Wilcoxon signed-rank test, at the 5% level of significance, to investigate whether the median number of words remembered by the 18-year-old males is greater than that for the 65-year-old males.