Mean

n

Median

STDEV

Cp Cpk % out of tolerance

Min/Max

Compare with

Calculate Difference

Diff mean normally

Diff median not normally

Diff variation normally

Diff variation not normally

Normally test

Correlation

Regression

Kurtosis

Skewness

For commercial use

75 EURO

To calculate if there is a significant difference between variation of the two data-sets. It calculates the F-test between this column and the comparing column.

- The smaller the p value is the more likely there is a significant difference in the variation of the data-sets.
- Develve uses the commonly accepted value of p < 0.05 for significance.
- For a good power (0.8 in Develve) the sample size for both data sets must be bigger than the minimum sample size calculated.
- For a good F-test the data-sets must be normally distributed see Anderson Darling normality test.
- If the data set is not normally distributed see "What to do with not normally distributed data". The Levene test is the not normally distributed counter part of the F-test.

- RedData-set is not normally distributed
- GreenNo significant difference
- YellowSignificant difference
- OrangeSample size to small

Where s1 is the smallest of the comparing STDEV values.

With the F value and the degrees of freedom can the program calculate the p value.

This results in the degrees of freedom out of the table, the Minimum sample size is

This results in the degrees of freedom out of the table, the Minimum sample size is

= STDEV smallest variation

= STDEV biggest variation

Degrees of freedom

- The difference in variance between data set A and B is not significant (Row F test p >0.05) and the sample size is to small (Row min Samples 240).
- The difference in variance between data set A and C is significant (Row F test p <0.05) and the sample size is big enough.
- The difference in variance between data set A and D is not significant (Row F test p >0.05) and the sample size is big enough.

Data file

- http://en.wikipedia.org/wiki/F-test_of_equality_of_variances
- http://en.wikipedia.org/wiki/F-test
- http://www.itl.nist.gov/div898/handbook/prc/section3/prc32.htm
- http://www.itl.nist.gov/div898/handbook/eda/section3/eda359.htm