About this calculator
When to use this
Use the normal distribution for quantities whose histogram is bell-shaped: heights, test scores, measurement errors, and (thanks to the Central Limit Theorem) sample means. Enter the mean and standard deviation, then shade the region you care about.
Probability or cutoff?
- A probability (area): "What percent of scores are above 80?" This is normalcdf on the TI-84.
- A cutoff (value): "What score marks the top 10%?" This is invNorm. Remember invNorm wants the area to the left, so the top 10% means a left area of 0.90.
With mean 0 and standard deviation 1, this is the standard normal distribution, so values are z-scores.