Question 974222: The proportions of defective parts produced by two machines were compared, and the following data were collected. Determine a 99% confidence interval for p1 - p2. (Give your answers correct to three decimal places.)
Machine 1: n = 149; number of defective parts = 16
Machine 2: n = 145; number of defective parts = 6
Lower Limit:
Upper Limit:
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! This is a 2-sample proportion test
99% CI= difference +/- z*SE for 2 proportions.
The proportions are 0.107 and 0.041 for each.
The SE is the sqrt (proportions*(`1-p)/n) for each
99%CI (-0.012, 0.144)
The confidence interval contains 0, so with 99% confidence one can say that the parameter, whatever it is, lies within an interval that contains 0 and therefore can be 0, or no difference. There is no probability involved. The parameter is either in the interval or it is not. If we constructed 100 different CIs, 99 of them would contain 0. We just don't know which one the data would fit.
Calculator: it is Stat-Calc-2 sample proportion test, inputting the n and the x (defective parts).
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