Chapter 6.1 & 6.2

Curves and Distributions

Properties of Normal Curve

  1. Curve is bell shaped with highest point over the mean µ
  2. Symmetrical curve with line through µ
  3. Curve approaches the horizontal axis but never touches or crosses it
  4. The inflection( transition) points between cupping upward and downward occur above µ + ơ and µ - ơ
  5. The area under the entire curve is 1

Empirical Rule

  • 68%=1 standard deviation
  • 95%=2 standard deviation
  • 99.7%=3 standard deviation

Control Chart

Control charts combine graphic and numerical descriptions of data with probability distributions

Out of Control Signals

If the x distribution is continuing in more or less the same manner, we say it is in statistical control. If it is not, we say it is out of control.

Standard Scores

Number of standard deviations an observation or datum is above the mean