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A factory produces cheap plastic rulers. The length of each ruler is on average 12 inches...

A factory produces cheap plastic rulers. The length of each ruler is on average 12 inches long, with a standard deviation of 0.05 inches. The distribution of ruler lengths is normal. Use proper notation and words, as needed, to show how you solve each part. For any variables you use, be sure to state what they represent.

  1. One ruler is selected at random. What is the probability it will be between 11.97 and 12.02 inches?

  2. What is the z-score of the 90th percentile?

  3. A sample of 40 rulers is selected. What is the probability the mean length of the sample will be between 11.97 and 12.02 inches?

Math   Statistics-And-Probability   
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