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The p-value is the chance-value and is always between 0 and 1, or in percentages between 0 and 100%.

Throwing up a dime and watching which side (head or coin) is visible when it lands on the floor will end up half of the time with head upwards and half of the time with coin upwards. So the chance that the head will appear is 50%. This is written as: p = .50. (By the way and of course, the change on a/the coin is 50% too.)

Throwing up a dice and the change number 1 will be on top is 1 out of 6. That is 16.6666%. This is written as p = 0.166666.

Changes are always between 0 and 1. A 0 means no chance on success and 1 (or 100%) means 100% chance of success.

In statistics three p-values are used

In statistics worldwide only three p-values are used: p = 0.05 (95%), p = 0.01 (99%) or p =0 .001 (99.9%). Although these values are completely arbitrary, do not use other values because nobody will take you seriously.

Now you could say that there are also p values of 0.025 (97.5%), p = .005 (99.5%) and p = .0005 (99.95%). These are the p values for two-sided tests and these p values are the halves of the first three. Combined (that is doubled) are still 5, 1 and 0.1%.

Related topics to p-value

• Normal distribution
• t-distribution
• Chi square distribution
• F-distribution
• Degrees of freedom

Analyze your data properly and quickly. Read these manuals and use our SPSS-tutorials

• The statistical test procedure
• Presenting statistical results

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