Question

Scientists want to estimate the mean weight of mice after they have been fed a

special diet. From previous studies, it is known that the weight is normally

distributed with standard deviation 4 grams. How many mice must be weighed so

that a 95% confidence interval will have margin of error of 0.4 grams?

Write only an integer as your answer.

Answer 1

n = 484

Explanation:

If Confidence Interval CI = 95 % then α = 5% and α/2 = 2,5 %

α/2 = 0,0125

MOE for normal distribution is:

MOE = z * σ/√n

For α/2 = 0,0125 ⇒ z(score) = -2,2

MOE = |-2,2| * 4/√n

0,4*√n = 8,8

√n = 8,8 / 0,4

√n = 22

n = 484