•   Arithmetic mean is also known as average. It is the sum of all the numbers divided by the number of numbers.

•   Median is the middle value in the list of numbers written in ascending or descending order.

•   Mode is the most frequently occurring value in the data set.

•   A Normal Distribution is perfectly symmetrical (not skewed). It means Mean = Mode = Median.

•   A distribution is skewed if one tail is longer than another. These distributions are sometimes called asymmetric distributions. These are of two types:

1. If Mode < Mean, then the data is skewed to the right.

2. If Mode > Mean, then the data is skewed to the left.