Data Collection Basics: Learn It 2

Sample and Statistic

Since surveying an entire population is often impractical, we usually select a sample to study.

sample

A sample is a smaller subset of the entire population, ideally one that is fairly representative of the whole population.

We will discuss sampling methods in greater detail in a later section.  For now, let us assume that samples are chosen in an appropriate manner.  If we survey a sample, say [latex]100[/latex] first-year students at your college, and find the average amount of money spent by these students on textbooks, the resulting number is called a statistic.

statistic

A statistic is a value (average, percentage, etc.) calculated using the data from a sample.

Statistic vs Parameter

You can view the transcript for “Statistic vs Parameter & Population vs Sample” here (opens in new window).

You can view the transcript for “Parameter vs Statistic” here (opens in new window).

You can view the transcript for “Populations, Samples, Parameters, and Statistics” here (opens in new window).

A researcher wanted to know how citizens of Tacoma felt about a voter initiative. To study this, she goes to the Tacoma Mall and randomly selects [latex]500[/latex] shoppers and asks them their opinion. [latex]60\%[/latex] indicate they are supportive of the initiative. What is the sample and population? Is the [latex]60\%[/latex] value a parameter or a statistic?