Chapter 6 Section 1 & 2
Landon Cormier
Properties of Normal Curve
2. Curve is symmetrical about a vertical line through the mean
3. curve approaches horizontal axis but never touches or crosses it
4. inflection(transition) points between cupping upward and downward
Mean and Standard Deviation
-mean is the highest point in the middle
-a whole standard deviation is 1 spot on each side of the mean
Empirical Rule
- approximately 68% of the data values will lie within 1 standard deviation on each side of mean
- approximately 95% of the data values will lie within 2 standard deviation on each side of mean
- approximately 99.7% of data values will lie within 3 standard deviation on each side of mean
Making a Control Chart
1. find the mean and standard deviation of x by:
A. using past data from a period during which the process was "in control" or
b. using specified "target" values for mean and standard deviation
2. create a graph in which the vertical axis represents x values and the horizontal axis represents time.
3. Draw a horizontal line a height of the mean
4. Plot the variable x on the graph in time sequence order. Use line segments to connect the points in time sequence order
Out of Control Signals
2. a run of nine consecutive points on one side of the center line
3. at least 2 of 3 consecutive points lie beyond the second deviation level on the same side of center line
Standard Scores
- a standard score close to zero tells us the measurement is near the mean of distribution
- positive standard score tells us the measurement is above the mean
- negative standard score tells us the measurement is below the mean