Find Sample Size From Confidence Interval. In this applet we construct confidence intervals for the mean of a Normal population distribution. Each interval is based on a SRS of size nThe dot marks the sample mean which is.
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It also represents the number of variables or observations. AL 1 degree of confidence 2. Therefore a sample of size 77 will ensure our margin of error for our confidence interval is no greater than 5.
N z 2 p 1 - p e 2.
σ is the population standard deviation of the data set. If the population standard deviation cannot be used then the sample standard deviation s can be used when the sample size is greater than 30. Therefore a sample of size 77 will ensure our margin of error for our confidence interval is no greater than 5. Where z 1645 for a confidence level α of 90 p proportion expressed as a decimal e margin of error.
