Solutions_Activity_08

# Solutions_Activity_08 - SOLUTIONS TO ACTIVITY SET 8...

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SOLUTIONS TO ACTIVITY SET 8 Activity 8.1 Suppose the amount students at PSU spent on textbooks this semester is a normal random variable with mean μ= \$360 and standard deviation σ = \$90. a. Use the empirical rule for bell-shaped data to determine intervals that will contain about 68%, 95% and 99.7% of amounts spent on textbooks by PSU students. Show work for each interval. 68% will be in interval 360± 90, or \$270 to \$450 95% will be in interval 360± (2×90), or \$180 to \$540 99.7% will be in interval 360± (3×90), or \$90 to \$630 b. With Minitab, find the cumulative probability for \$300. Use Calc>Probability Distributions>Normal , enter the mean and standard deviation, click on “Input Constant” and enter 300 in the adjacent box. [Note: The notation for the probability you’re finding is P(X ≤ \$300).] x P( X <= x ) 300 0.252493 c. Write a sentence interpreting the value found in the previous part that would be understood by somebody with no training in statistics. About 25% of PSU students spent less than \$300 on textbooks this semester.

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## This note was uploaded on 10/08/2010 for the course STAT 200 at Penn State.

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Solutions_Activity_08 - SOLUTIONS TO ACTIVITY SET 8...

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