A few analysis of relationship that has been considered has to do with single variable of continuous and ordinal nature. Point Biserial correlation is way too different as it entails having a binary or dichotomous variable.
In the course of this guide, I shall tend to explain point biserial correlation in details. If you are a statistician, then this guide is for you.
What is point Biserial correlation?
Point Biserial correlation analysis is an analysis that express the relationship between a continuous level variable and a dichotomous variable.
Dichotomous variable are of norminal scale with only two values. They can also be referred to as binary variable.
Binary variables or dichotomous variables are variable that express two values. Example of binary variables are;
Gender- it value is male or female
Reaction- it's values are react or non reacting.
Age- it values are elderly or non elderly
Does it sound clear?
Yes if it does, then we can proceed.
Correlation Analysis measures the strength of relationship between variables In a range of -1 to 0 to +1.
Negative 1 (-1)
When the relationship carries a negative sign, it entails that if two variables are considered in the relationship e.g variable X and variable Y.
The higher variable X or increase in variable X will lead to a simultaneous decrease in variable Y or decrease in variable X will lead to a similar decrease in variable Y.
Zero correlation
Zero correlation entails that there is no relationship at all between the variables in consideration. Then the relationship is said to be zero or tends towards zero.
Am sure this is quite understood.
Positive correlation (+1)
Positive correlation entails that the relationship between the variables in consideration can be explained as thus, an increase in variable X will lead to a simultaneous increase in variable Y and vice versa.
Example of questions that can be answered using point Biserial Correlation
The following questions can be answered using point Biserial correlation in SPSS
Does wealth depends on education in certain parts of the world?
What is the relationship between wealth and education level ( literate / non literate)
According to statistics solutions manual, this example was gotten from there.
What is the relationship between taking traditional (drug / pharmaceutical drug) and the length of someones life?
You can see both questions got binary variables.
How to Carryout Point Biserial Correlation Analysis In SPSS
To carryout correlation analysis, check for the relationship first between the dichotomous and continous variable using a box plot.
Onlike other correlation analysis, SPSS will find the relationship between the continous level variable of the binary variable so you also have to include it.
It is the box plot that can be used for the indication of the relationship between the dichotomous variable and the continous level variable easily.
Buy when you want to find the relationship in a rela analysis, use the continous variable of the binary variable choosen on your scale.
Conclusively
This article has been able to present a brief about point Biserial correlation analysis to be the analysis that show the relationship between a continuous variable and a binary variable.
References
S.C Gupta (2012), Fundamentals of statistics.
Statistics solutions, Statistical Analysis, "Point Biserial Correlation Analysis"