Question

The 68–95–99.7 rule tells us how to find the middle 68%, 95% or 99.7% of a normal distribution. Suppose we wanted to find numbers A and B, so that the middle 80% of a standard normal distribution lies between A and B, where A is less than B. One of the answers below is NOT true of A and B. Which answer is NOT true?

Twenty percent of the distribution lies below A. 0 To get the middle 80%, we would have A = -B. 3 B is approximately 1.28 Ten percent of the distribution lies above B.

Answer 1

Twenty percent of the distribution lies below A is not true.

Explanation:

The middle 80% of a standard normal distribution lies between the points A and B, then the remaining 20% is equally divided by 2 and 10% of it lies below A, 10% lies above B.

Attached graph below, dark area represents middle 80%, 10% white area is right of the dark area and 10% is left of the dark area.