(7) Sampling distribution for a population's mean (a) If the random sample is large (30 or more), then according to the Theorem the x sampling distribution is normal/bell-shaped. (b) Even for small-sized random samples (less than 30), as long as the population from which the random sample was taken has a normal distribution, then the shape of the X sampling distribution is (c) Before estimating a population's mean with a Confidence Interval, if the size of a random sample is small (less than 30), then statisticians must check to make sure that the random sample has no outliers/extreme values. That's because the mean is to extreme values. Answer is either "resistant" or "not resistant"