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Normal Probability is perfect for anyone taking (or teaching!) statistics and probability.

For each calculation this app gives:

• the appropriate z-scores
• the resulting probability
• a graph highlighting the specific area under the Normal Distribution

Probabilities and z-scores are calculated to the same number of decimal places as shown in your textbook and their tables. This allows rapid comparisons and helps you stay on track.

Probabilities are calculated for Individual Scores and Sample Means.

Additionally, probabilities for the standard normal distribution are easily calculated by setting the population mean to zero and the population standard deviation equal to one.

New in Version 1.3: Critical Values

Critical Values are used for confidence interval construction and for hypothesis testing.

This app calculates Critical Values for all values of alpha α and for all three of the cases: left tail area, right tail area, and both left & right tail area. Additionally, a graph highlighting the specific area under the Normal Distribution is provided.

Normal Probability was written by a statistics professional with more than 20 years of educational experience. Give yourself an edge by getting this app!

Send Questions or Comments about Normal Probability to

*New* Watch these YouTube videos to see this app in action!

Examples Part 1 - Probability -
Examples Part 2 - Critical Values -