1. Weighing Errors A scale is designed so that when items are weighed, the errors in the indicated weights are normally distributed with a mean of 0 g and a standard deviation of 1 g. (If the scale reading is too low, the error is negative. If the scale reading is too high, the error is positive.)

a. If an item is randomly selected and weighed, what is the probability that it has an error between 0.5 g and 0.5 g?

b. If 16 items are randomly selected and weighed, what is the probability that the mean of the errors is between 0.5 g and 0.5 g?

c. What is the 90th percentile for the errors?

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312 Chapter 6 Normal Probability Distributions