Question : Suppose we wish to design a study to investigate the effects of loud music on teenagers’ ability to concentrate. We know from previous studies that the standard deviation of time to complete this task is 3.4 minutes. How many subjects would be required to ensure with 90% confidence that the generated estimate is within 1 minute of the true mean time required? Solution : E =1 , where E = margin of error, s.d. = σ = 3.4 s.e. = σ / √n = 3.4 / √n Zα = 1.645 at 90% confidence. also, E = s.e.× Zα = 1 => 3.4 × 1.645 / √n = 1 => √n = 3.4 × 1.645 = 5.593 => n = 32 (approx.) Ans: the Sample size necessary is 32
Posted on: Sat, 15 Mar 2014 06:01:19 +0000
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