A SAMPLE FROM THE NORMAL DISTRIBUTION

Even if a variable is normally distributed in the population, a sample from the population does not necessarily have a distribution that is exactly normal. Samples vary, so the distributions for individual samples vary as well. However, if a sample is reasonably large and it comes from a normal population, its distribution should look more or less normal. The majority of statistical packages do offer this functionality. For example, the SPSS software package provides additional information so that the experimenter can actually see the misses of the distribution. Specifically, SPSS/PC + places colons and dots on the histogram to show a true normal distribution. The colons and dots indicate how many cases would be expected in the intervals if the distribution were exactly normal with the same mean and standard deviation as the sample. A colon appears in place of the bar if the normal distribution falls inside the histogram. A dot appears if the normal distribution falls outside the histogram (beyond the end of the bar).