Introduction:

Correlation is a statistical technique used to measure the relationship between two variables. It shows how strong or weak the association is between the two variables.

Method:

The quickest method to find correlation between two variables is by using a correlation coefficient. There are different types of correlation coefficients, including Pearson correlation coefficient, Spearman correlation coefficient, and Kendall correlation coefficient.

Pearson correlation coefficient:

This is the most commonly used correlation coefficient. It measures the linear relationship between two continuous variables. It ranges from -1 to +1, where -1 indicates a perfect negative correlation, +1 indicates a perfect positive correlation, and 0 indicates no correlation.

To find the Pearson correlation coefficient, follow these steps:

1. Calculate the means of both variables.
2. Calculate the standard deviations of both variables.
3. Calculate the covariance between the two variables.
4. Divide the covariance by the product of the standard deviations.

Spearman correlation coefficient:

This correlation coefficient measures the relationship between two variables when one or both variables are ordinal. It ranges from -1 to +1, where -1 indicates a perfect negative correlation, +1 indicates a perfect positive correlation, and 0 indicates no correlation.

To find the Spearman correlation coefficient, follow these steps:

1. Rank both variables from lowest to highest.
2. Calculate the difference between the ranks for each observation.
3. Calculate the Spearman rank correlation coefficient using the formula.

Kendall correlation coefficient:

This correlation coefficient measures the relationship between two variables when one or both variables are ordinal. It ranges from -1 to +1, where -1 indicates a perfect negative correlation, +1 indicates a perfect positive correlation, and 0 indicates no correlation.

To find the Kendall correlation coefficient, follow these steps:

1. Rank both variables from lowest to highest.
2. Count the number of concordant and discordant pairs.
3. Calculate the Kendall rank correlation coefficient using the formula.

Conclusion:

In general, the Pearson correlation coefficient is the quickest and easiest method to find correlation between two continuous variables. However, if one or both variables are ordinal, the Spearman or Kendall correlation coefficient may be more appropriate.

Multiplication