Question

A marketing research company wishes to know how many energy drinks adults drink each week. They want to construct a 95% confidence interval with an error of no more 0.08. A consultant has informed them that a previous study found the mean to be 5.9 energy drinks per week and found the standard deviation to be 1.3. What is the minimum sample size required to create the specific confidence interval?

Answer 1

Solution :

Given that,

standard deviation = = 1.3

margin of error = E = 0.08

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.960

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

= ((1.960 * 1.3) / 0.08 )2

= 1014

Sample size = 1014