Question

How many observations should a time study analyst plan for in an operation that has a standard deviation of 1.3 minutes per piece if the goal is to estimate the mean time per piece to within .2 minutes with a confidence of 78.5 percent. thanks i will rate the question.

Answer 1

solution :

Given that,

standard deviation =   =1.3

Margin of error = E = 0.2

At 78.5% confidence level

= 1 -78.5%  

= 1 - 0.785 =0.215

/2 = 0.1075

Z/2 = Z0.1075 = 1.24

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

n = ( 1.24 *1.3 / 0.2 )2

n =64.9

Sample size = n =65