Page 4 - Lesson note-5-Ch 14 Statistics ( Measure of Central Tendency)

Mean = 7
Therefore, the mean of all the factors of 20 is 7.

(v) We know that
All prime numbers between 50 and 80 = 53, 59, 61, 67, 71, 73 and 79
Mean = sum of numbers/ total numbers
Mean = (53 + 59 + 61 + 67 + 71 + 73 + 79)/7
Mean = 463/7
1
Mean =66
7
1
Therefore, the mean of all prime numbers between 50 and 80 is 66 .
7
Example 4. If the mean of five observations x, x + 2, x + 4, x + 6, x + 8 is 13, find
the value of x and hence find the mean of the last three observations.
Solution:
Number of observations = 5 It is given that mean = 13
[x + (x + 2) + (x + 4) + (x + 6) + (x + 8)]/5 = 13
5x + 20 = 13 (5)
5x + 20 = 65
5x = 45
x = 9

By substituting the value of x
The last three observations are 9 + 4 = 13, 9 + 6 = 15, 9 + 8 = 17
Mean of last three observations = (13 + 15 + 17)/3
= 45/3 = 15
Therefore, the mean of last three observations is 15