# 6.1 and 6.2

### It's math, yo - James Avault and Alec Tull

## Important Properties of a Normal Curve

1. The curve is bell shaped, with the highest point over the mean.

2. The curve is symmetrical about a vertical line through the mean.

3. The curve approaches the horizontal axis but never touches or crosses it.

4. The inflection points between cupping upward and downward occur above the mean + o and the mean - o.

5. The area under the entire curve is 1.

## Empirical Rule says that 68% of the data will lie in one standard deviation side of the mean, 95% of the data is in two standard deviations on each side of the mean, and 99.7% lie within all three deviations on each side of the media.

Control Charts were made in the 1920s by the Bell Telephone Co. These combine graphic and numerical descriptions of data with with probability distributions.