The diameter of dot produced by the printer is normally distributed with mean diameter of 0.002 inch. Assume that the specifications require the dot diameter to be between 0.0014 and 0.0026 inch.
a. If the probability that the dot meets specifications is to be 0.9973, what standard deviation is needed?
b. Suppose that the standard deviation of size of a dot is 0.0004 inch. If the probability that the dot meets specifications is to be 0.9973, what specifications are needed? Suppose that the specifications are to be selected symmetrically around mean of 0.002.