Confidence level and risk level are two ways of looking at the same thing. The confidence level tells you how certain you can be that any significant differences between the columns tested are due to some external factor rather than being due to chance. The risk level is the opposite of the confidence level and tells you how likely it is that any differences are due to chance rather than being significant for some other reason.

The sum of the confidence level and the risk level is 100, so a confidence level of 95% implies a risk level of 5%, and vice versa.

Quantum can test the significance of statistical values at a number of confidence levels. Acceptable values in Quantum for all tests except the Newman-Keuls test are 99, 95, 90, 85, 80, 75 and 68. Acceptable values for the Newman-Keuls test are 99, 95 and 90 only.

If you do not specify a confidence level, Quantum uses the default of 95% confidence.

To specify the confidence level you want for a particular test, add the option:

to the tstat statement. If you want to set a global confidence level for all tests, place this option on the a statement instead.

The option requires you to specify one confidence level, but allows an optional second level. If you specify a second level it must be lower than the first level and must be separated from it by a comma.

For the proportions, means and Newman-Keuls tests, Quantum checks first for significance at the higher level and prints an uppercase letter if the value is significant at that level. If the test fails, Quantum tests for significance at the lower level and prints a lowercase letter if the value is significant at that level. Otherwise, no letter is printed.

The same rules apply to the paired preference test, but significance at a given level is shown by the letter S (higher level) or s (lower level) as appropriate.

The significant net difference test uses the higher level only and silently ignores any lower level that is set.

The automatic footnote reports the risk level at which significance was tested. You can specify your own titles that show the risk level or the confidence level using the options <<risk>> and/or <<conf>> on the tt statement that creates the title.