The Rockwell hardness of certain metal pins is known to have a mean 52 and a standard deviation 4. Assume that the distribution of all such pin hardness measurements is known to be normal. If a random sample of 16 pins is obtained, what is the probability that the average hardness is at most 48? (a) P(? ? 48) = 0.0456 (b) P(? ? 48) = 0.0228 (c) P(? ? 48) = 0.3085 (d) P(? ? 48) = 0.1587
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SEM = 4 / √16 SEM = 4 / 4 SEM = 1 Show more…
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