Chapter 6.1 & 6.2
By: Davon Parker
Properties of Nominal Curve
2. The curve is symmetrical about a vertical line through u.
3. The curve approches the horizontal axis but never touches or crosses it.
4. The inflection (transition) points between cupping upward and downward occur above u + o and u - o.
5. The area under the entire curve is 1.
M & O
1. Find the mean u and standard deviation o of the x distibutuion by
(a) using past data from a period during which the process was "in control" or
(b) using specified "target" values for u and o.
2. Create a graph in which the vertical axis resprents x vaules and the horizontal axis represents time.
3.Draw a horizontal line at height u and horizontal, dashed control-limit lines at u +_ 2o and u= +_ 3o.
4. Plot the variables x on the graph in time sequence order. Use line segments to connect the points in time sequence order.
Out of Control Siganls
2. Out of Control Signal II: A run of nine consecutive points on one side of the center line (the line at target value u)
3.Out control Signal III: At leaast two of three consecutive points lie beyond the 2o level on the same side of the center line
Z- Scores- Calculating
Approximately 68% of the data values will lie within 1 standard deviation on each side of the mean.
Approximatley 95% of the data values will lie within 2 standard deviations on each side of the mean.
Approximately 99.7% (or almost all) of the data values will lie within 3 standard deviations on each side of the mean.
Using Z- scores & Appendex w/ Probabilities
2. Treat any area to the left of a z value greater than 3.49 as 1.000.