A random sample of 100 observations is to be drawn from a population with a mean of 40 and a standard deviation of 25. the probability that the mean of the sample will exceed 45 is.. ?
A - 0.4772
B - 0.4207
C - 0.0793
D - 0.0228
E - not possible to compute based on the information provided
i think that the answer is C but im not positive. i need help. will vote best answer (:
A - 0.4772
B - 0.4207
C - 0.0793
D - 0.0228
E - not possible to compute based on the information provided
i think that the answer is C but im not positive. i need help. will vote best answer (:
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Mean μ = 40
Standard deviation σ = 25
Standard error σ / √ n = 25 / √ 100 = 2.5
standardize xbar to z = (xbar - μ) / (σ / √ n )
P(xbar > 45) = P( z > (45-40) / 2.5)
= P(z > 2) = 0.0228
(from normal probability table)
Standard deviation σ = 25
Standard error σ / √ n = 25 / √ 100 = 2.5
standardize xbar to z = (xbar - μ) / (σ / √ n )
P(xbar > 45) = P( z > (45-40) / 2.5)
= P(z > 2) = 0.0228
(from normal probability table)
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I'd go with C.