1. The problem statement, all variables and given/known data A company produces batches of 1800 axle shafts . These are tested to determine the proportion of those with too rough surface according to the standards set in the industry. The quality control department of a sample of 150 axle shafts in a lot and concluded that there are between 15 % and 25 % of the axle shafts in this set that are outside the norms . Calculate the confidence level associated with this estimate. 2. Relevant equations tn-1,sigma/2=(ME)/((s/sqrt(n))* (sqrt(1-(n/N))) (1-sigma)=tcdf(-tn-1,sigma/2,+tn-1,sigma/2,n-1) 3. The attempt at a solution Known variable: N = 1800 n=150 [15%,25%] ---> average= (15+25)/2 =20% or 0.20 ME = (25-15)/2 = 5% or 0.05 Unknown variable: (1-sigma) Average of N Standard Deviation of n I am stuck here, I cannot continue without knowing SD.