 Hi and welcome to the session. Today we will learn about arithmetic mean. In our present day life we need information in the form of numerical figures which is called data. This data can be related to the profits of a company during some year, the monthly which is earned by the workers in a factory, marks obtained by the students of a class etc. So before collecting data it should be clear to us that for what purpose we want to use that data. Now once we have collected the data we must organize it in a tabular form so that it can help us at any point of time. Now let us see what is average. Average is a number that represents or shows the central tendency of a group of observations or data. Now different forms of data need different forms of representative or central value to describe it. So here one of the representative value arithmetic mean. Now let us see what is arithmetic mean. So the arithmetic mean denoted as AM or mean or average is defined as sum of all observations upon number of observations. Let us take an example. Suppose we are given some observations that is 30, 25, 40, 35 and 65 and we need to find out the mean or arithmetic mean of these observations. Then first of all we will find the sum of all observations which will be equal to 30 plus 25 plus 40 plus 35 plus 65 which is equal to 195 and here the number of observations is equal to 5 as there are 5 observations. So now mean is given by sum of all observations upon number of observations. So this will be equal to 195 upon 5 which will be equal to 39. So mean of these given observations is 39. Now if you will see it carefully then you will notice that mean always lies between the greatest the smallest observations. If you find out the mean of any two numbers say 5 and 13 which will be equal to 5 plus 13 upon 2 that is 9. So here 9 lies between 5 and 13. Now our next topic is range. If we are given few observations and we need to find out the range of observations then this will be equal to highest observation minus lowest observation. Let's take an example for this. Let's take the same observations which we took in our last example that is 30, 25, 40, 35 and 65. Here we need to find the range of these observations. So to find out range first of all we will arrange these observations in ascending order. Thus we have 25, 30, 35, 40 and 65. Now range is given by highest observation minus lowest observation and here 65 is the highest observation and 25 is the lowest observation. So range will be equal to 65 minus 25 which will be equal to 40. With this we finish this session. Hope you must have understood all the concepts. Goodbye, take care and have a nice day.