Qualitative Analysis

RES-866_Module_6_DQ_1_-_Grand_Canyon_University.docx

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The sample size determination depends on 4 factors namely Population Size, Margin of Error (Confidence Interval), Confidence Level and Standard of Deviation. Sine no sample is perfect, I decide a value of Margin of error which tells me how much error I can allow. The confidence interval determines how much higher or lower than the population mean you are willing to let your sample mean fall. Confidence Level tells me how confident I am that the actual mean falls within your confidence interval. It can be 90%, 95% or 99%.

I know that ME = z(a/2)*SE = z(a/2) * (sd/sqrt(n)). This implies, n = z(a/)^2 * sd / ME^2. For level of significance 0.05, I am 95% confident about my results. Z(a/2) = z(0.05/2) = 1.96. I choose 0.5 as standard deviation, and a margin of error (confidence interval) of +/- 5%, then sample size is calculated as:

1.96^2 * 0.5 / 0.05^2

=768.32

=738 (approximately)