4. Lei investigated the effect of word length on short-term memory capacity - AQA - A-Level Psychology - Question 4 - 2022 - Paper 1

The dependent variable (DV) in this investigation is the number of words recalled correctly by participants from the list of 14 words.

To calculate Mann-Whitney U:

1. Rank the scores from both conditions:

   • Condition A: Monosyllabic Words

     Number of Words Recalled	Rank
     9	16.5
     8	13.5
     9	16.5
     10	19.5
     10	19.5
     11	20.5
     9	16.5
     9	16.5
     Total	145.5

   • Condition B: Polysyllabic Words

     Number of Words Recalled	Rank
     5	5
     7	11
     6	8
     7	11
     9	16.5
     16	17
     6	8
     1	1
     Total	64.5

2. Calculate U values:
   • For Condition A: U_A = R_A - rac{n_A(n_A + 1)}{2} = 145.5 - rac{8(8 + 1)}{2} = 145.5 - 36 = 109.5
   • For Condition B: U_B = R_B - rac{n_B(n_B + 1)}{2} = 64.5 - rac{8(8 + 1)}{2} = 64.5 - 36 = 28.5
3. Use the smaller U value: $U = 28.5$

Using the calculated U value (28.5), we compare it to the critical value for a one-tailed Mann-Whitney test with 8 participants in each condition. The critical value at p ≤ 0.05 is 27. Since 28.5 is greater than 27, we conclude that Lei's data are not significant at p ≤ 0.05.