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Coal is carried from a mine in West Virginia to a power plant in Pittsburgh in hopper cars on a long train. The automatic hopper car loader is set to put 75 tons of coal into each car. The actual weights of coal loaded into each car are normally distributed with an average of 75 tons and a standard deviation of 0.8 ton.

What is the chance 20 cars chosen at random will have an average load of less than 74.7 tons of coal?


1.Enter the average of the box:


2.Enter the SD of the box:


3.Enter the number of draws from the box:

4.Calculate the expected value for the average (EVave):

5.Calculate the standard error for the average (SEave):Round to three decimal places.

6.Calculate the chance 20 cars chosen at random will have an average load of less than 74.7 tons of coal. Round your answer to one decimal place.

  • Stats () - ,

    You can answer 1-3 just by citing the data.

    EVave = sample mean

    SEave = SEm = SD/√n

    Z = (score-mean)/SEm

    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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