Some probabilities for normal distributions

We now give a few probabilities that hold for all normal distributions.

A more precise version of the second probability is

You often meet the value "1.96" in statistics!

Use the pop-up menu to display the probabilities of values (highlighted areas) within 1, 2 and 3σ of µ

70-95-100 rule of thumb and the normal distribution

These probabilities conform closely to the 70-95-100 rule that we presented as a rule-of-thumb for numerical data sets with reasonably symmetric 'bell-shaped' distributions.

Indeed, the normal probabilities are the basis of the earlier rule-of-thumb!