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In 2020, the average charge of tax preparation was $95. Assuming a normal distribution and a standard deviation of $10, use the approximate areas beneath the normal curve, as discussed in this section, to answer the following questions.

What proportion of tax preparation fees were between $75 and $115?

A) 0.84

B) 0.34

C) 0.955

D) 0.75

  • Statistics -

    This will be within two standard deviations of the mean. To show this, use z-scores.

    Formula is this:
    z = (x - mean)/sd
    z = (75 - 95)/10 = ?
    z = (115 - 95)/10 = ?

    I'll let you finish the calculations. Remember that one z-score is below the mean and one is above the mean.

    I hope this will help get you started.

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