Question

A student wanted to estimate the number of chocolate chips in a commercial brand of cookie. he sampled 100 cookies and found an average of 10.5 chips per cookie. if we assume the standard deviation is 8, what is a 99% confidence interval for the average number of chips per cookie?

Answer 1

To find the interval we use the formula:
x'+/-2.58σ/√n
where:
x'= sample mean=10.5
2.58=table value at 99% confidence
σ=population standard deviation=8
n=100

substituting the values we get:
(10.5+/-2.58*0.08)/√100
=(10.5+/-2.064)/10
=(10.5+2.064,10.5-2.064)/100
=(0.126, 0.084)