# Finite Math Examples

Find the Variance of the Frequency Table
Step 1
Reorder the classes with their related frequencies in an ascending order (lowest number to highest), which is the most common.
Step 2
Find the midpoint for each group.
Step 2.1
The lower limit for every class is the smallest value in that class. On the other hand, the upper limit for every class is the greatest value in that class.
Step 2.2
The class midpoint is the lower class limit plus the upper class limit divided by .
Step 2.3
Simplify all the midpoint column.
Step 2.4
Add the midpoints column to the original table.
Step 3
Calculate the square of each group midpoint .
Step 4
Simplify the column.
Step 5
Multiply each midpoint squared by its frequency .
Step 6
Simplify the column.
Step 7
Find the sum of all frequencies. In this case, the sum of all frequencies is .
Step 8
Find the sum of column. In this case, .
Step 9
Find the mean .
Step 9.1
Reorder the classes with their related frequencies (ƒ) in an ascending order (lowest number to highest), which is the most common.
Step 9.2
Find the midpoint for each class.
Step 9.3
Multiply the frequency of each class by the class midpoint.
Step 9.4
Simplify the column.
Step 9.5
Add the values in the column.
Step 9.6
Add the values in the frequency column.
Step 9.7
The mean (mu) is the sum of divided by , which is the sum of frequencies.
Step 9.8
The mean is the sum of the product of the midpoints and frequencies divided by the total of frequencies.
Step 9.9
Simplify the right side of .
Step 10
The equation for the standard deviation is .
Step 11
Substitute the calculated values into .
Step 12
Simplify the right side of to get the variance .