In a study of memory recall, 8 students from a large psychology class were selected at random and given 10 minutes to memorize a list of 20 nonsensical words. Each was asked to list as many of the words as he or she could remember both 1 hour and 24 hours later. The data are as shown in the accompanying table.
Student 1 2 3 4 5 6 7 8
1 hour later 14 13 19 7 12 11 17 15
24 hours later 9 4 14 5 9 7 12 11
Use these data to estimate the difference in mean number of words remembered after 1 hour and after 24 hours. Use a 90% confidence interval. (Use μd = μ1 hour later − μ24 hours later. Use a table or technology. Round your answers to two decimal places.)
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