100-Metodos-de-Qualidade-Total

156 100 METHODS FOR TOTAL QUALITY MANAGEMENT
Method 69
Basic statistics
Purpose
The mean, median, mode, range and standard deviation are ways of
summarizing and describing large volumes of data. The first three are
measures of location; the last two are measures of spread.
When to use
When looking for patterns in data or when trying to compare large volumes
of data, these parameters give statistically based measures that aid
decision-taking.
How to use
The mean
The mean is the simple arithmetic average of all the data points. To
calculate the mean, add together all the points and divide by the number of
points in the sum.
The mean is usually written X (pronounced X bar). The formula is
X =
I(xI + X2 + X3 + ....... Xn)
n
where there are n points called XI to Xn.
As an example, the following list gives the voltage derived from a circuit
having variability due to poor tolerance control:
There are 37 points in total.
1.1 1.2 1.2 1.3
1.3 1.3 1.4 1.4
1.4 1.4 1.5 1.5
1.5 1.6 1.6 1.6
1.7 1.7 1.7 1.8
1.8 1.8 1.9 1.9
1.9 1.9 1.9 2.0
2.0 2.0 2.0 2.1
2.1 2.1 2.2 2.2
2.3