Question

A poultry researcher conducted a small pilot study to investigate a new diet for improving weight gain in week-old chicks. The results from 9 chicks fed with the new diet was a mean weight gain of 74.2 g with standard deviation 2.16 g.

For her full study she would like to estimate mean weight gain with a margin of error of 0.5 g at 95% confidence but for ethical reasons would like to keep the number of chicks at a minimum. The number of chicks she should use is how many chicks?

Answer 1

Solution :

Given that,

Population standard deviation = = 2.16

Margin of error = E = 0.5

At 95% confidence level the z is,

= 1 - 95%

= 1 - 0.95 = 0.05

/2 = 0.025

Z/2 = Z0.025 = 1.96  

sample size = n = [Z/2* / E] 2

n = [1.96 * 2.16 / 0.5]2

n = 71.69

Sample size = n = 72