Normal and Skewed distributions

The Normal Distribution Curve

Skewed distributions Sometimes “outliers” or scores which are either much higher or much lower than the others, can really affect the mean, making it much higher or lower than it would be without those scores. In these cases, you might be better off using the median as your measure of central tendency as it will describe the data set more effectively. These outliers will mean that you do not get a nice neat normal distribution when you plot your scores

Skewed distributions

Negative (or left) skew When we talk about skew, we look at where on the graph the long tail lies If the long tail is on the left, we say the skew is negative It is heading towards the negative end of the x axis You will see that the mean is less than the median which is less than the mode

Positive (or right) skew If the long tail is on the right, we say the skew is positive It is heading towards the positive end of the x axis You will see that the mode is less than the median which is less than the mean