Sample size and margin of error. The margin of error for the one-sample t confidence interval depends on the confidence level, the standard deviation, and the sample size. Fix the confidence level at 95% and the standard error at s = 1 to examine the effect of the sample size n. Find the margin of error for sample sizes of 5 to 100 by 5s. That is, let n = 5, 10, 15, . . . , 100. Plot the margins of error versus the sample size and summarize the relationship.