Compute the Range

Range = high score - low score
 

Choose i

There must be between 10 and 20 class intervals

Create Class Intervals

All lower apparent limits must be a multiple of i

All class intervals must be the same size

The highest class interval must contain the highest score

The lowest class interval must contain the lowest score
 

Compute Real Limits

Upper real limit = upper apparent limit + .5 units

Lower real limit = lower apparent limit - .5 units
 

Tally Frequencies

Find the Midpoint