1. Normal and Skewed distributions

2. The Normal Distribution Curve

3. 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

4. Skewed distributions

5. 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

6. 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