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toothpaste666
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Homework Statement
- A national safety council wishes to estimate the proportion of automobile accidents that involve pedestrians. How large a sample of accident records must be examined to be 99% certain that the estimate does not differ from the true proportion by more than 0.03? Answer the question if
(a) the council believes that the true proportion is 0.2.
(b) no information about the true proportion is given.
The Attempt at a Solution
α = .01 , α/2 = .005, z.005 = 2.575
a) n = p(1-p) [zα/2/E]^2
= (.2)(.8)[2.575/.03]^2 = 1179
b) n = .25[zα/2/E]^2 = (.25)[2.575/.03]^2 = 1842
is this correct?