rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.4. (round your answers to four decimal places.) (a) if the distribution is normal, what is the probability that the sample mean hardness for a random sample of 16 pins is at least 51? (b) what is the (approximate) probability that the sample mean hardness for a random sample of 44 pins is at least 51?
