This slide describe the stepwise methods of hand calculation of Pearson correlation coefficient. it involves the hypothesis making and testing. Two methods are explained, one with covariance and second with direct formula. The formula derivation is also explained and at the last the graphic presentation is also given to show the line of fitness and direction of the correlation.
3. THE RELATION BETWEEN COVARIANCE AND
CORRELATION
• A covariance is the relation between two continuous variables.
• When covariance is divided by the product of standard deviations of x and y, it
gives the correlation coefficient. Covariance is the unstandardized while
correlation is the standardized.
5. EXERCISE-1: Basic understanding of correlation
formula
1. What will happen to the correlation coefficient, when the standard deviation of
(x) and (y) decreases?
2. What will happen to the correlation coefficient, if the standard deviation of (x)
and (y) increases?
3. What will be the impact on the value of standard deviation, if sample increase
and decrease?
6. A PRACTICAL EXAMPLE
• An examination was conducted among 11 students of M.Sc. of research
methodology. We have the theory marks (20) and practical marks (10).
• We are interested to know, whether students are having the equal command in
theoretical and practical of research method? Whether there is any association or
relation between their theoretical and practical knowledge of research
methodology? Based on this assumption, we made two hypotheses.
• Ha: There will be a significant association between theory and practical marks of
students
• H0: There will be no significant association between the marks of theory and
practical examination.
• To test these hypotheses, we need to calculate the Pearson’s correlation.
23. INTERPRETATION OF THE RESULT
• Pearson’s correlation coefficient (r) = 0.93
• Sample size =n =11, degree of freedom (df) = n-2 = 11-2 =9
• The critical value of Pearson Correlation Coefficient (p≤ 0.05) =
0.602
• The critical value of Pearson Correlation Coefficient (p≤ 0.01) =
0.735
• Since the (r = 0.93) is greater than 0.602 and 0.735, therefore,
correlation coefficient (r=0.93) is statistically significant at (p≤ 0.01)
with confidence interval 99.99%
25. THE FINAL RESULT
• Since the (r = 0.93) is greater than 0.602 and 0.735, therefore, correlation coefficient
(r=0.93) is statistically significant at (p≤ 0.01) with confidence interval 99.99%
• Ha: There will be a significant association between theory and practical marks of students
• H0: There will be no significant association between the marks of theory and practical
examination.
• Now, there is a highly significant positive correlation between the marks of theory and
practical examinations of M.Sc. Students. Therefore, the alternative hypothesis is accepted
and the null hypothesis is rejected.
• It is proved that students have equal knowledge in theory and practical and they are
applying their theoretical knowledge in practical also.
26. Thanks for your attention!
In the next session, we will learn about the Spearman’s
rank Correlation
keep learning !!!