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 6 grams. How many mice must be weighed so that a 95% confidence interval will have margin of error of 0.5 grams?

Answer 1

Given that,

standard deviation = = 6

margin of error = E = 0.5

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 =1.96

Sample size = n = [(Z/2 * ) / E]2

= ((1.96 * 6 ) /0.5 )2

= 553.19

Sample size = 554