# STP 231 Lecture Notes - Lecture 19: Tanning Bed, Central Limit Theorem, Sampling Distribution

## Document Summary

For random sample of sufficiently large size, the sampling distribution of the sample mean is approximately normal with mean and standard deviation /sqrt(n) Randomization: data values must be sampled randomly. Independence assumption: the sampled values must be mutually independent. 10% rule: the sample is no more than 10% of the population. The sample size must be at least 30. If the population is normally distributed, you do not need to worry about sample size. If we were to draw a curve to fit the information, it will be a symmetric normal curve. Each number represents a sample mean of one of the many samples selected. When we put all of these sample means together, we make the sample normal distribution curve. A health club recently added tanning booths in addition to a weight room, pool, and racquetball courts. For insurance purposes, an employee maintains careful records of the length of time each member spends in a tanning booth.