 Hi and welcome to the session. It is just as a following question. The question says, find the mean deviation about the medium for the data in exercises three and four. This is the data given to us. Before solving this question, we should know the steps which are involved in the calculation of mean deviation about medium. In the first step, we have to calculate the medium which is obtained by first arranging the data in ascending or descending order and then applying the following rule. Calculate the number of observations. If number of observations is even, then median is equal to n by 2 observation plus n by 2 plus 1 at observation divided by 2. And if number of observations is odd, then median is equal to n plus 1 by 2 at observation, let that median be a. In the second step, we find the deviation of each xi from a, that is x1 minus a, x2 minus a and so on. In the third step, we find the absolute value of each deviation, that is, drop the minus sign if it is there, that is, mod of x1 minus a, mod of x2 minus a, so on, mod of xn minus a. And then in the last step, we find the mean of the absolute values of the deviations. And this mean is the mean deviation about median, that is, mean deviation about median is equal to 1 by n into summation i goes from 1 to n, mod xi minus m where m is equal to median of the given data. So, keeping all these rules in mind, let us now begin with the solution. We will first find the median of the given data. So, let us first arrange this data in ascending order. Now, the given data in ascending order is 10, 11, 11, 12, 13, 14, 16, 16, 17, 17, 18. Now, calculate the number of observations. Number of observation is 12, n is equal to 12 and 12 is even. So, median is equal to 12 by 2 observation plus 12 by 2 plus 1 observation divided by 2. And this is equal to sixth observation plus seventh observation divided by 2. And the sixth observation is 13 and seventh observation is 14. So, we have 13 plus 14 by 2 and this is equal to 27 by 2. 27 by 2 is 13.5. Now, let us calculate A is equal to median of the given data that is 13.5. Calculate deviation of each xi from A. First observation is 10 and A is equal to 13.5. So, we have 10 minus 13.5 and this is equal to minus 3.5. Second observation is 11 and median is equal to 13.5. So, we have 11 minus 13.5 and this is equal to minus 2.5. For in the same pattern, we have calculated deviation of each xi from A. Absolute value of each deviation, absolute value of minus 3.5 is 3.5, absolute value of minus 2.5 is 2.5, absolute value of minus 0.5 is 0.5, absolute value of 0.5, 2.5 and 3.5 is 0.5, 2.5 and 3.5, absolute value of minus 2.5 is 2.5, absolute value of minus 1.5 is 1.5, absolute value of 0.5, 2.5, 3.5 and 4.5 is 0.5, 2.5, 3.5 and 4.5. Mean deviation about median. Now, mean deviation about median is equal to 1 by n into summation i goes from 1 to 12 xi minus n. This is equal to 1 by 12 into 3.5 plus 2.5 plus 0.5 plus 0.5 plus 2.5 plus 3.5 plus 2.5 plus 1.5 plus 0.5 plus 2.5 plus 3.5 plus 4.5. This is equal to 28 by 12 and 28 by 12 is 2.33. Hence, the required answer is 2.33. So, this completes the session. Bye and take care.