Question

The average time a subscriber of a local newspaper The News spends reading it is 24...

  1. The average time a subscriber of a local newspaper The News spends reading it is 24 minutes. Assume that the times are normally distributed and the standard deviation is 10 minutes.
  1. Compute the probability that a subscriber spends more than 30 minutes reading the paper.
  1. Find the range of reading times for the middle 90% of the subscribers.

[Hint: First,     nd zc such that P ( zc < z < zc) = 0:90.]

  1. The average time was calculated from a sample of 20 subscribers. Compute the probability that this mean value is more than 30 minutes.

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