Math

Q1. A population has a mean of µ = 80 with σ = 20.

a. If a single score is randomly selected from this population, how much distance, on average, should you find between the score and the population mean?
20 because the standard deviation is 20
b. If a sample of n = 4 scores is randomly selected from this population, how much distance, on average, should you find between the sample mean and the population mean?
10 because 20/square root of 4 equals 10
c. What is the probability that sample mean will be less than 70 for a sample of 16 scores?
I don't know what formula to use for this one???

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  1. Z = (score-mean)/SEm

    SEm = SD/√n

    Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.

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  2. population has a mean of µ = 80 with σ = 20.
    a. Would a score of X=70 be considered an extreme value (out in the tail) in this sample?
    b. If the standard deviation were σ = 5, would a score of X=70 be considered an extreme value?

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