In: Statistics and Probability
Let X equal the excess weight of soap in a "1000-gram" bottle.
Assume that the distribution of XN(μ,180).
What sample size is required so that we have 95% confidence that
the maximum error of the estimate of μ is 1.7?
Sample size required= ?
given , σ² =180
σ=√σ² = √180 = 13.4164
sampling error , E = 1.7
Confidence Level , CL= 95%
alpha = 1-CL = 5%
Z value = Zα/2 = 1.960 [excel
formula =normsinv(α/2)]
Sample Size,n = (Z * σ / E )² = ( 1.960
* 13.4164 / 1.7 ) ²
= 239.3
So,Sample Size
needed= 240