Question

9.

For a normal distribution with mean 20 and standard deviation 5, approximately what percent of
the observations will be between 5 and 35?
A. 50%
B. 68%
C. 95%
D. 99.7%

Answer 1

Answer: D. 99.7%

Explanation:

Scores that lies within the first deviation(1σ) =

(20 - 5) to (20 + 5) → 15 to 25

Scores that lies within the second deviation(2σ) =

(20 - 5 - 5) to (20 + 5 + 5) → 10 to 30

Scores that lies within the third deviation(3σ) =

(20 - 5 - 5 - 5) to (20 + 5 + 5 + 5) → 5 to 35

As shown by the distribution graph below, 99.73% of the scores lies within the third deviation(3σ).