Correlation | Class 11 Economics Notes

Techniques for Measuring Correlation

Correlation between two variables can be studied using three main techniques: scatter diagrams, Karl Pearson's coefficient of correlation, and Spearman's rank correlation coefficient. A scatter diagram is a graphical method where values of two variables are plotted as points on a graph. It visually shows the nature and direction of the relationship but does not provide a numerical measure. Karl Pearson's coefficient is a numerical measure of the strength and direction of a linear relationship between two variables measured on interval or ratio scales. It assumes the relationship is linear and is sensitive to outliers. Spearman's rank correlation is used when variables are ordinal or when precise measurement is difficult, such as in cases involving subjective attributes like honesty or beauty. It measures the association between ranks assigned to the data rather than the raw data itself. Each method has its own use depending on the nature of data and the relationship.

📊 Diagram: Scatter diagrams show points scattered around upward or downward sloping lines indicating positive or negative correlation, or no clear pattern indicating no correlation.

🧪 Activity: Collect data on height, weight, and marks scored by students and draw scatter diagrams to observe relationships.

🔗 Connection: Leads to detailed calculation and interpretation of Karl Pearson's coefficient.