thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Data & Analytics · Foundational

Empirical Rule

The 68-95-99.7 rule: in a normal distribution about 68%, 95% and 99.7% of values lie within 1, 2 and 3 standard deviations of the mean.

Definition

The rule gives quick estimates of how unusual a value is and underlies three-sigma control limits.

Example

Mean 100, SD 15: about 95% of values lie between 70 and 130.

Exam tip

Memorize 68-95-99.7; it appears constantly in statistics questions.

Related terms