Correlation | Class 11 Economics Notes
By ConceptScroll Team · Published on 17 July 2026 · 2 min read
Correlation – this guide gives you a concise, exam-ready overview of Correlation from Class 11 Economics, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
Properties of Correlation Coefficient
The correlation coefficient r has several important properties that aid in its interpretation and calculation. First, r is a pure number without any units, meaning it is independent of the units of measurement of the variables. A positive r indicates a direct relationship where variables move in the same direction, while a negative r indicates an inverse relationship where variables move in opposite directions. The value of r always lies between -1 and +1; values outside this range indicate errors in calculation. The coefficient is unaffected by changes in origin (adding a constant) or scale (multiplying by a positive constant), which allows for simplified calculation methods like the step deviation method. If r = 0, the variables are uncorrelated linearly, though other types of relationships may exist. Perfect correlation occurs at r = +1 or r = -1, indicating exact linear relationships. High absolute values of r (close to 1) indicate strong linear relationships, while values close to zero indicate weak or no linear relationships. It is essential to remember that correlation does not imply causation; external factors or time lags may influence the observed correlation.
📊 Diagram: Scatter diagrams showing perfect positive and negative correlation with points exactly on a line, and imperfect correlation with points scattered around a line.
🔗 Connection: Leads to numerical examples illustrating calculation and interpretation of r.
Frequently asked questions
The unit of correlation coefficient between height in feet and weight in kgs is (i) kg/feet (ii) percentage (iii) non-existent
The correlation coefficient is a measure of the degree of linear relationship between two variables and is a pure number without any units. Hence, the unit of correlation coefficient is non-existent.
The range of simple correlation coefficient is (i) 0 to infinity (ii) minus one to plus one (iii) minus infinity to infinity
The range of the simple correlation coefficient is from -1 to +1.
If $ r_{xy} $ is positive the relation between $ X $ and $ Y $ is of the type (i) When $ Y $ increases $ X $ increases (ii) When $ Y $ decreases $ X $ increases (iii) When $ Y $ increases $ X $ does not change
If r_xy is positive, it means that as Y increases, X also increases.
If $ r_{xy} = 0 $ the variable $ X $ and $ Y $ are (i) linearly related (ii) not linearly related (iii) independent
If r_xy = 0, variables X and Y are not linearly related.
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