CH.6 part 1&2 Prob and Stat
Control Chart
The control chart is a graph used to study how a process changes over time. Data are plotted in time order.
Z-Score
A Z-Score is a statistical measurement of ascore's relationship to the mean in a group ofscores. A Z-score of 0 means the score is the same as the mean. A Z-score can also be positive or negative
Empirical Rule
The empirical rule states that for a normal distribution, nearly all of the data will fall within three standard deviations of the mean.
This rule has 3 parts:
- 68% of data falls within the first standard deviation from the mean.
- 95% fall within two standard deviations.
- 99.7% fall within three standard deviations.
Normal Curve
- The normal curve is symmetrical about the mean μ;
- The mean is at the middle and divides the area into halves;
- The total area under the curve is equal to 1;
- It is completely determined by its mean and standard deviation σ
μ - Sample Mean σ - Standard Deviation
Calculating Standard Deviation:
- Work out the Mean (the simple average of the numbers)
- Then for each number: subtract the Mean and square the result
- Then work out the mean of those squared differences.
- Take the square root of that and we are done