A2.L.1Normal & z-scores01/04
Normal distribution and z-scores.
Step01of 04
The normal distribution is the bell-shaped curve that describes many naturally occurring measurements (heights, test scores, measurement errors). It's symmetric around the mean μ with spread determined by the standard deviation σ.
Empirical rule (68-95-99.7).
| Within ±1 SD of mean | →about 68% of data |
| Within ±2 SD of mean | →about 95% |
| Within ±3 SD of mean | →about 99.7% |