Stats Review: Population vs. Sample

In statistics it is important to make the distinction between a population and a sample. Statistical equations vary slightly between the two and knowing what type of data you will be working with will help you choose the right equation.

Definitions

Population :        All objects or beings pertaining to group are considered for statistical purposes.

Sample :               Only a select group pertaining to a population is selected for statistical purposes.

Examples :

a)      A survey is given to all the inhabitants of New York City.

(Answer : Population)

b)      A survey is given to 5000 people at random in New York City.

(Answer : Sample)

c)       3 apples are taken from a basket and weighed in order to find the weight of the average apple.

(Answer : Sample)

d)      All apples are taken from the basket and weighed in order to find the average weight of an apple from that particular basket.

(Answer : Population)

e)      A person weighs himself 5 times to get his current weight.

(Answer : Population)

In statistic a population is denoted with N and a sample with n. For example, a population containing 1000 entities would be written as N=1000 and a sample containing 10 entities would written as n=10. When using statistical equations make sure you are using the right equations. Equations containing N are for populations only and equations containing n are for samples only. Confusing the two will lead to erroneous statistical results.