SOLUTION: A normal distribution of weekly income has a mean of $250 and a standard deviation of $20. Approximately what proportion of people earn between $240 and $260 a week?

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Question 414490: A normal distribution of weekly income has a mean of $250 and a standard deviation of $20. Approximately what proportion of people earn between $240 and $260 a week?
Answer by stanbon(57984) About Me  (Show Source):
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A normal distribution of weekly income has a mean of $250 and a standard deviation of $20. Approximately what proportion of people earn between $240 and $260 a week?
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z(240) = (240-250)/20 = -1/2
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z(260) = (260-250)/20 = +1/2
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Proportion(240<= x <=260) = P(-1/2 <= z <=1/2) = 0.3829
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Cheers,
Stan H.