CORRELATION AND TYPES

Correlation is the relationship between quantitative / qualitative variables

Correlation coefficient (r) is the value is the relationship between two variable. It can also be said as the Measure of correlation.

Range of correlation: -1 to 1

Types of correlation:

1. Pearson correlation

2. Spearman correlation

3. Kendall rank correlation

4. Point-Biserial correlation

Types of correlation coefficient:

1. No correlation — when correlation coefficient (r)=0
2. Positive correlation — when correlation coefficient (r)>0
3. Negative correlation — when correlation coefficient (r)<0

Types of correlation based on Variable:

1. Simple correlation — between two variables
2. Partial correlation — partially among many variables
3. Multiple correlation — among three or more variables

Types of correlation based on change in ratio between the variables:

1. Linear

X: 10 ,20 ,30 ,40 ,50

Y:20 ,40 ,60 ,80 ,100

These two variables(X,Y) bear a constant ratio

2. Non Linear

X: 10 ,20 ,30 ,40 ,50

Y:5 ,18 ,23 ,31 ,44

These two variables(X,Y) do not bear a constant ratio

Interpretation of r value:

if r value

• Exactly –1. A perfect downhill (negative) linear relationship
• –0.70. A strong downhill (negative) linear relationship
• –0.50. A moderate downhill (negative) relationship
• –0.30. A weak downhill (negative) linear relationship
• 0. No linear relationship
• +0.30. A weak uphill (positive) linear relationship
• +0.50. A moderate uphill (positive) relationship
• +0.70. A strong uphill (positive) linear relationship
• Exactly +1. A perfect uphill (positive) linear relationship