The lengths of a lawn mower part are approximately normally distributed with a given mean mu is equal to 4 in. and standard deviation sigma is equal to 0 point 2 in. What percentage of the parts will have lengths between 3 point 8 in. and 4 point 2 in.?

The interval from 3.8 in. to 4.2 in. is 0.2 in. below and above the mean of 4 in. Since the standard deviation is 0.2 in., this is the range within one standard deviation of the mean. In a normal distribution, about 68% of values lie within one standard deviation, so the answer is D) 68 percent.

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