The arithmetic mean (or simply the mean) of a list of numbers is the sum of all the members of the list divided by the number of items in the list.

Learn how to calculate the Mean.

The standard deviation is a measure of the dispersion of a set of values. It measure how widely spread the values in a data set are. If many data points are close to the mean, then the standard deviation is small; if many data points are far from the mean, then the standard deviation is large. If all data values are equal, then the standard deviation is zero. A useful property of standard deviation is that, unlike variance, it is expressed in the same units as the data.

Learn how to calculate the Standard Deviation.

The mode is the value that occurs the most frequantly in a data set or a probability distribution.

Example: A= { 1,2,3,4,5,5,6,7,8,9,9,9}

The mode is the number 9 that repeats 3 times in the data set.

If two (or more) data repeat the same number of times than the data set is called bimodal (or multimodal if there is more than two datas repeating the same number of times).