Finding the Appropriate z Value for the Confidence Interval Formula (Using a Table) @jbstatistics

Uploaded April 2013 | Updated September 2026, 2 hours ago

I show how to find the appropriate z value (using the standard normal table) when calculating a confidence interval. The version of the table used in this video gives the area to the left of the z value (and not the area between 0 and z).

For those that use R, below is the R code to find the values (see the video for illustrations).

z value for a 95% interval:
qnorm(.975)
[1] 1.959964

z value for a 75% interval:
qnorm(.875)
[1] 1.150349

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