h accuracy level desired in percent of the job element, expressed as a decimal (5% = 0.05) = z number of standard deviations required for desired level of confidence (e.g. for 90% confidence, z = 1.65) = s standard deviation of the initial sample = mean of the initial sample x = n required sample size = s = xi x 2 n 1 For the first operation, s = seconds (round your response to two decimal places) . was found to be seconds. h is given as %. The value of z for the given confidence level = . 1.95 x 8.60 5 1.65 Using the above values, n for the first operation = observations (round your response to the immediate higher whole number). 56 One would be required to repeat the above steps for the remaining three operations and then find the biggest required number of the observations to be able to determine the number of observations for the overall process. The number of observations that are required for a % confidence level within % accuracy = (round your response to the