Balbharati Maharashtra State Board 11th Commerce Maths Solution Book Pdf Chapter 5 Correlation Ex 5.1 Questions and Answers.

## Maharashtra State Board 11th Commerce Maths Solutions Chapter 5 Correlation Ex 5.1

Question 1.

Draw a scatter diagram for the data given below and interpret it.

Solution:

Since all the points lie in a band rising from left to right.

Therefore, there is a positive correlation between the values of X and Y respectively.

Question 2.

For the following data of marks of 7 students in Physics (x) and Mathematics (y), draw scatter diagram and state the type of correlation.

Solution:

We take marks in Physics on X-axis and marks in Mathematics on Y-axis and plot the points as below.

We get a band of points rising from left to right. This indicates the positive correlation between marks in Physics and marks in Mathematics.

Question 3.

Draw a scatter diagram for the data given below. Is there any correlation between Aptitude score and Grade points?

Solution:

The points are completely scattered i.e., no trend is observed.

∴ there is no correlation between Aptitude score (X) and Grade point (Y).

Question 4.

Find correlation coefficient between x andy series for the following data:

n = 15, \(\bar{x}\) = 25, \(\bar{y}\) = 18, σ_{x} = 3.01, σ_{y} = 3.03, \(\sum\left(x_{\mathrm{i}}-\bar{x}\right)\left(y_{\mathrm{i}}-\bar{y}\right)\) = 122

Solution:

Here, n = 15, \(\bar{x}\) = 25, \(\bar{y}\) = 18, σ_{x} = 3.01, σ_{y} = 3.03, \(\sum\left(x_{\mathrm{i}}-\bar{x}\right)\left(y_{\mathrm{i}}-\bar{y}\right)\) = 122

Question 5.

The correlation coefficient between two variables x and y are 0.48. The covariance is 36 and the variance of x is 16. Find the standard deviation of y.

Solution:

Given, r = 0.48, Cov(X, Y) = 36

Since \(\sigma_{X}^{2}\) = 16

∴ σ_{x} = 4

∴ the standard deviation of y is 18.75.

Question 6.

In the following data, one of the values of y is missing. Arithmetic means of x and y series are 6 and 8 respectively. (√2 = 1.4142)

(i) Estimate missing observation.

(ii) Calculate correlation coefficient.

Solution:

(i) Let X = x_{i}, Y = y_{i} and missing observation be ‘a’.

Given, \(\bar{x}\) = 6, \(\bar{y}\) = 8, n = 5

∴ 8 = \(\frac{35+a}{5}\)

∴ 40 = 35 + a

∴ a = 5

(ii) We construct the following table:

Question 7.

Find correlation coefficient from the following data. [Given: √3 = 1.732]

Solution:

Question 8.

The correlation coefficient between x and y is 0.3 and their covariance is 12. The variance of x is 9, find the standard deviation of y.

Solution:

Given, r = 0.3, Cov(X, Y) = 12,

\(\sigma_{X}^{2}\) = 9

∴ \(\sigma_{\mathrm{X}}\) = 3

∴ the standard deviation of y is 13.33.