Variance

Step 1: Calculate the midpoint ( ) for each class interval.
4-8:
8-12:
12-16:
16-20:

Step 2: Calculate the necessary sums using a table. Let be the frequency.

Step 3: Calculate the mean ( ).

Step 4: Calculate the variance ( ). The formula for variance is .

Step 5: Compare the result with the given options. The calculated variance is 19, which matches option (C).