Uploaded February 2012 | Updated September 2026, 2 hours ago
I have an updated and revised version of this video available at youtu.be/JYP6gc--sGQ. Please watch the improved version.
Interpreting a confidence interval for the population mean mu. Some reasonable interpretations are discussed, as are some common misconceptions. Many of these concepts hold for confidence intervals for other parameters.
I have an updated and revised version of this video available at youtu.be/JYP6gc--sGQ. Please watch the improved version.
Interpreting a confidence interval for the population mean mu. Some reasonable interpretations are discussed, as are some common misconceptions. Many of these concepts hold for confidence intervals for other parameters.

![What Factors Affect the Margin of Error? (In a Confidence Interval for One Mean)
A look at the effect of various factors (the standard deviation, the sample size, and the confidence level) on the margin of error of a confidence interval for the population mean.
For those that use R, below I give the R code to find the values given in this video.
Z value for a 90% interval (see my other videos for a more detailed explanation of the rationale):
qnorm(.95)
[1] 1.644854
Z value for a 95% interval:
qnorm(.975)
[1] 1.959964
Z value for a 99% interval:
qnorm(.995)
[1] 2.575829 What Factors Affect the Margin of Error? (In a Confidence Interval for One Mean)](https://i.ytimg.com/vi/NQtcGOhUWB4/mqdefault.jpg)








