1.MEAN 2.MODE 3.MEDIAN

If x 1, x 2, x 3, x n are observations with respective frequencies f 1, f 2, f 3, …, f n, then mean is given as X = Mean =

Methods to find mean: 1.Direct method : Class mark = For a class interval 10 – 20, class mark is 15. For a class interval , class interval is 25.

1.Direct method : X =

EXERCISE A survey was conducted by a group of students as a part of their environment awareness programme, in which they collected the following data regarding the number of plants in 20 houses in a locality. Find the mean number of plants per house. Number of plants Number of houses

Class interval Class mark x Frequency f fx

Class interval Class mark x Frequency f fx TOTAL20

Here, So, Mean = = ANS. The mean number of plants is 8.1 per house. = 8.1

2. Consider the following distribution of daily wages of 50 workers of a factory. Daily wages ( in Rs) Number of workers Find the mean daily wages of the workers of the factory by using an appropriate method.

Class interval Class mark x Frequency f fx TOTAL50

Class interval Class mark x Frequency f di = x- 150fi x di TOTAL = 50 = ? Let assumed mean A = 150 Let assumed mean A = 150

So, mean = A + ( assumed mean method) = ( ) = = So, the mean daily wage of the workers = Rs

4. Thirty women were examined in a hospital by a doctor and the number of heart beats per minute were recorded and summarised as follows. Find the mean heart beats per minute for these women choosing a suitable method. Number of heart beats per minute Number of women

Class interval Class mark x Frequency f di = x- 75.5fi x di TOTAL =30 = ?

Class interval Class mark x Frequency f d = x- 75.5f x d TOTAL =30 = ?

So, mean = A + ( assumed mean method) = ( ) = = 75.9 Ans. The mean heart beats per minute = 75.9

5. In a retail market, fruit vendors were selling mangoes kept in packing boxes. These boxes contained varying number of mangoes. The following was the distribution of mangoes according to the number of boxes. Number of mangoes Number of boxes Find the mean number of mangoes kept in a packing box. Which method of finding mean did you choose?

Class interval New CI. Class mark x Frequenc y f di = x fi x di TOTAL =30 = ?