This occurs even though the population distribution may not be normal in shape. We also saw that area under the curve implies probability. Thus, if the sampling distribution of the mean is normal we can establish the probability of obtaining a particular sample mean. Formal Example Let us look at an example that will set the stage for the format we will use when testing a hypothesis. We will use one from your book.
Animal studies suggest that the anticholinergic drug physostigmine improves memory.
Studies with humans typically report that we remember an average of seven of 15 words given an 80-minute retention interval. These studies also suggest a standard deviation for the population of two. The drug has no effect on memory. The drug has an effect on memory. Assumptions Sample is randomly selected.