Population concepts
A census is an official count of a country's population, often collecting details like age, sex, and occupation, and is essential for economic planning (e.g. estimating demand for schools, hospitals, and jobs). Population growth rate measures how fast a population is changing, driven by birth rates, death rates, and net migration.
Example 1: A country's population grows from 40 million to 42 million in one year. Find its population growth rate.
Growth rate = .
Basic statistical measures
The mean (average) of a data set is found by adding all the values and dividing by the number of values.
Example 2: Find the mean of the following weekly incomes: ₦5,000, ₦7,000, ₦6,000, ₦8,000.
Mean = naira.
Index numbers
An index number expresses a value relative to a fixed base period, usually set to 100, making it easy to see percentage changes over time. A common example is a price index, which tracks how the general price level has changed since the base year -- if a price index rises from 100 to 115, average prices have risen by 15% since the base year.