I have exams in two weeks. So I am confused that during which sums which formula is applicable?
Aayushi, the question will specify the method (Karl pearson's or spearman) using which the numerical will be solved. The procedure and formula for each method is already covered in our study material. You can follow the given link to learn the same.
https://www.meritnation.com/cbse/class11-commerce/studymaterial/economics/statistics-for-economics/correlation/443_2499_6439#slide1_Methods of Measuring Correlation Scattered Diagram and Karl Pearson's Coefficient of Correlation
And , you can use the formula of any method i.e assumed mean method, step deviation method etc to solve your question in case of karl Pearson's method if question does not specify any particular method.
https://www.meritnation.com/cbse/class11-commerce/studymaterial/economics/statistics-for-economics/correlation/443_2499_6439#slide1_Methods of Measuring Correlation Scattered Diagram and Karl Pearson's Coefficient of Correlation
And , you can use the formula of any method i.e assumed mean method, step deviation method etc to solve your question in case of karl Pearson's method if question does not specify any particular method.