Statistics (Ex – 15.2)
Find the mean and variance for each of the data in Exercises 1 to 5.
Question 1.
6, 7, 10, 12, 13, 4, 8, 12
Solution:
Here xi = 6, 7, 10, 12, 13, 4, 8, 12
∴ Σxi = 6 + 7 + 10 + 12 + 13 + 4 + 8 + 12 = 72
n = 8
Question 2.
First n natural numbers
Solution:
Here xi = 1, 2, 3, 4, ……….n
Question 3.
First 10 multiples of 3
Solution:
Here xi = 3, 6, 9, 12, 15, 18, 21, 27, 30,
Σxi = 3 + 6 + 9 + 12 + 15 + 18 + 21 + 24 + 27 + 30 = 165
n = 10
Question 4.
Solution:
Question 5.
Solution:
Question 6.
Find the mean and standard deviation using short-cut method
Solution:
Find the mean and variance for the following frequency distributions in Exercises 7 and 8.
Question 7.
Solution:
Question 8.
Solution:
Question 9.
Find the mean, variance and standard deviation using short-cut method.
Solution:
Question 10.
The diameters of circles (in mm) drawn in a design are given below:
Calculate the standard deviation and mean diameter of the circles.
[Hint: First make the data continuous by making the classes as 32.5 – 36.5, 36.5 – 40.5, 40.5 – 44.5, 44.5 – 48.5, 48.5 – 52.5 and then proceed.]
Solution: