Posted by Jessica on Wednesday, June 22, 2011 at 8:14pm.
95% interval = mean ± 1.96 SEm
SEm = SD/√(n-1)
Find the mean first = sum of scores/number of scores
Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance.
Standard deviation = square root of variance
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