Question

A consumer advocate wants to collect a sample of jelly jars and measure the actual weight of the product in the container. He needs to collect enough data to construct a confidence interval with a margin of error of no more than 5 grams with 99?% confidence. The standard deviation of these jars is usually 6 grams. Estimate the minimum sample size required.

Answer 1

Solution :

Given that,

standard deviation = = 6

margin of error = E = 5

At 99% confidence level the z is ,

  = 1 - 99% = 1 - 0.99 = 0.01

/ 2 = 0.01 / 2 = 0.005

Z_/2 = Z_0.005 = 2.576

Sample size = n = ((Z_/2 * ) / E)²

= ((2.576 * 6) / 5)²

= 9.55 = 10

Sample size = 10