Question

A toy manufacturer wants to know how many new toys children buy each year. A sample of 520520 children was taken to study their purchasing habits. Construct the 85%85% confidence interval for the mean number of toys purchased each year if the sample mean was found to be 6.66.6. Assume that the population standard deviation is 22. Round your answers to one decimal place.

Answer 1

solution:-
given that mean = 6.6
standard deviation = 2
n = 520

85% critical value for z is 1.44

confidence interval formula

=> x +/- z * s/sqrt(n)

=> 6.6 +/- 1.44 * 2/sqrt(520)

=> 6.6 +/- 0.1
=> (6.5 , 6.7)