Meaning and types of correlation

correlation

1. Meaning and Types of Correlation Dr. Showkeen Bilal, Assistant Professor, GDC Pulwama

2. Correlation The word Correlation is made of Co- (meaning "together"), and Relation Correlation is a statistical tool that helps to measure and analyse the degree of relationship between two variables . It helps us in finding the degree or extent of quantitative relationship between two variables . Sir Francis Galton introduced correlation, but Karl Pearson provided the mathematical framework.

3. CORRELATION COEFFICIENT The measure of correlation is called the correlation coefficient .  The Coefficient of Correlation (r) is a measure of the strength of the linear relationship between two variables .   The degree of relationship lies between -1 and + 1 or range from ( -1 ≤ r ≥ +1 ).

4. Types of Correlation Positive Correlation: The correlation is said to be positive correlation if the values of two variables change in the same direction . As X is increasing, Y is increasing. As X is decreasing, Y is decreasing,

5. Negative Correlation: The correlation is said to be negative correlation when the values of variables change in opposite directions.  As X is increasing, Y is decreasing. As X is decreasing, Y is increasing.  

6. Methods of Studying Correlation  Scatter diagram method Karl Pearson’s coefficient of correlation Spearman’s coefficient of rank correlation Concurrent deviation method Partial correlation Multiple correlation

7. Karl Pearson's Coefficient of Correlation Most widely used measure of correlation   This method is also known as Pearson’s product moment method in honour of Karl Pearson(1857-1936 , who is said to be the inventor of this method. Karl Pearson’s Coefficient of Correlation is denoted by- ‘r ’ The coefficient of correlation ‘r’ measure the degree of linear relationship between two variables say x & y .  If r = +1, then the correlation between the two variables is said to be perfect and positive  If r = -1, then the correlation between the two variables is said to be perfect and negative If r = 0, then there exists no correlation between the variables

8. Spearman Rank Correlation  Spearman rank order correlation coefficient, named after Charles Spearman Charles Edward Spearman (1863 – 1945 ) was an English psychologist known for work in statistics, as a pioneer of factor analysis, and for Spearman's rank correlation coefficient. Spearman’s correlation is designed to measure the relationship between variables measured on an ordinal scale of measurement.  it uses ranks as opposed to actual values . It is also called as the Spearman’s rho (ℓ ) correlation.

9. Importance Of Correlation   Correlation helps to study the association between two variables. Coefficient of correlation is vital for all kinds of research work. It helps in establishing Validity or Reliability of an evaluation tool. It helps to ascertain the traits and capacities of pupils while giving guidance or counseling. Correlation analysis helps to estimate the future values.

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