Question 1169719: 3)Miss jones, the senior typist,made errors on 15 out of 125 pagesof typing, whilstMiss Smith made errors on 44 pages out of 255 pages of typing. Is Miss Jones’errorratesignificantly lower than Miss Smith’s?Why? Use 90% confidence interval to answer this question.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! J=0.12
S=44/255=0.1725
The difference between them is 0.0525
doing a 2 sample proportion
half-interval for 90%CI is 1.645* sqrt[(0.12*0.88/125)+(0.1725*0.8275/255)], sqrt term=0.0374
=0.0617
The 90% CI is difference+/- the half-interval
(-0.1142, 0.0092)
Because 0 is in the interval, we can be 90% confident that there is no significant difference between these two proportions. Stated another way, if they were part of the same population, these samples could occur by chance.
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