On the left is a distribution with a large and on the right one with a smaller. It is a bell-shaped curve with its mode (= mean and median because it’s symmetric, ) centred on its mean. The normal distribution’s shape is as shown in Figure 5.2.įigure 5.2: The normal distribution. For those with a bad math background, the letters in Equation (5.28) are:, , = mean and = standard deviation of the normal distribution. Without that factor we just have a bell-shaped curve with the area under the curve equal to one we have a probability function since the total probability is one. The factor is a normalization factor that ensures that the area under the whole curve is one: Its formula (which you will never have to use because we have tables and SPSS) is again:
Let us now take a detailed look at the normal distribution and learn how to apply it to probability problems (in sampling theory) and statistical problems.
