Number of cases of malaria detected in 10yrs are 100, 160, 190, 250, 300, 300, 320, 320, 550, 380. How to calculate the average number of cases per year-
In this question there is no extreme value.
When there is no extreme value, arithmetic mean is the most commonly used statistical average.
Option 'b' requires specific mention here -


Geometric means

Geometric mean is a type of average, which indicates the central tendency of a set of number.
It is similar to arithmetic mean, except that instead of adding the set of numbers and then dividing the sum by the count of numbers in the set, in geometric mean the numbers are multiplied and then nth root of the resulting product is taken (n is the count of numbers in the set).
Arithmetic mean
Geometric mean
Mode
Median