Point-Biserial Correlation Calculator
Measure the relationship between a two-group variable and a continuous one. Paste the 0/1 values and the matching continuous values in the same order.
Learn how to calculate it yourselfEnter your values
Results update as you type.
Point-biserial r
Check your inputs
Enter valid values to see your result. Use the field hints or open the data guide for help.
Calculate it yourself
Use binary group codes 0,0,1,1 with matching continuous values 1,3,5,7.
Follow this worked example, then repeat the steps with your own numbers.
Find the mean of each variable
Mean binary code = 0.5. Mean continuous value = 4.Center values and add products
Binary deviations = −0.5, −0.5, 0.5, 0.5. Continuous deviations = −3, −1, 1, 3. Sum of cross-products = 4.Divide by the combined spread
Sum of squared binary deviations = 1; continuous = 20. r = 4 ÷ √(1 × 20) ≈ 0.894. r² = 0.8.If needed, look up the significance test
t = r × √[(n − 2)/(1 − r²)] = √8 ≈ 2.828, with n − 2 = 2 degrees of freedom.Use a t table or spreadsheet to find twice the upper-tail probability beyond |t|. Point-biserial correlation is Pearson correlation with a 0/1 variable.
Use your PaperSurvey.io results
Export matched binary and numeric responses to calculate their point-biserial correlation here.
What point-biserial measures
The point-biserial correlation measures how strongly a two-group variable relates to a continuous one, for example whether answering a test item correctly relates to the total score. It is mathematically a Pearson correlation with one variable coded as 0 and 1, so it runs from minus 1 to plus 1 and is read the same way.
Formatting your data
Enter the binary variable as 0s and 1s, then the continuous values in the same respondent order. The two lists must be the same length. A positive result means the group coded 1 tends to have higher continuous scores.
Frequently asked questions
Where is this used in testing?
Item analysis uses point-biserial correlation as a discrimination index: it shows whether students who got an item right also scored higher on the test overall.
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