# Data Collection Basics

# Introduction

## What you’ll learn to do: Identify the various aspects of data collection

Data collection is something we should all have a general understanding of, especially now. The United States census is an example of a huge, data collection undertaking. The following video gives some background and information about the US census. https://www.youtube.com/watch?v=Vn4K3XoywlY In this lesson we will introduce some important terminology related to collecting data. When you are finished you will be able to identify the difference between terms like census and sample, parameter and statistic, quantitative and categorical data. In the following lessons we will rely on your understanding of these terms, so study them well!### Learning Outcomes

- Identify the population of a study
- Identify the difference between a census and a sample
- Determine whether a value calculated from a group is a statistic or a parameter
- Determine whether a measurement is quantitative or qualitative (categorical)

### Learning new Math vocabulary and notation

You've seen before that learning mathematics is similar to learning a new language -- it takes repetition and practice to obtain new vocabulary and symbols. Statistics has a rich, well-defined set of vocabulary and symbols particular to itself. The symbols and terms in this section may be completely unfamiliar to you or you may have seen them before in other contexts. Either way, you'll need to spend time with them to become fluent in their use in statistics.# Populations and Samples

Before we begin gathering and analyzing data we need to characterize the**population**we are studying. If we want to study the amount of money spent on textbooks by a typical first-year college student, our population might be all first-year students at your college. Or it might be:

- All first-year community college students in the state of Washington.
- All first-year students at public colleges and universities in the state of Washington.
- All first-year students at all colleges and universities in the state of Washington.
- All first-year students at all colleges and universities in the entire United States.
- And so on.

### Population

The**population**of a study is the group the collected data is intended to describe. Note: Sometimes the intended population is called the

**target population**, since if we design our study badly, the collected data might not actually be representative of the intended population.

### example

A newspaper website contains a poll asking people their opinion on a recent news article. What is the population?Answer: While the target (intended) population may have been all people, the real population of the survey is readers of the website.

*every*member of our population, the resulting number would be called a

**parameter**. For example, the average amount of money spent on textbooks by

*each and every*first-year student at your college during the 2009-2010 academic year would be parameter for that population.

### Parameter

A**parameter**is a value which describes the entire population.

### Census

A survey of an entire population is called a**census**.

**sample**to study.

### Sample

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

**statistic**.

### Statistic

A**statistic**is a value which describes a sample.

### example

The average weight of*all*adult Labradors is a parameter while the average weight of a

*sample*of 7 adult Labradors is a statistic.

### example

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 500 shoppers and asks them their opinion. Of those shoppers surveyed, 60% indicate they are supportive of the initiative. What is the population and the sample? Is the 60% value a parameter or a statistic?Answer: The sample is the 500 shoppers questioned. The population is less clear. While the intended (or target) population of this survey was likely all Tacoma citizens, the effective population was mall shoppers. There is no reason to assume that the 500 shoppers questioned would be representative of all Tacoma citizens. The 60% value was based on the sample, so it is a statistic.

### examples

**Example 1**: To determine the average length of fish in a lake, researchers catch 20 fish and measure them. What is the sample and population in this study?

Answer: The sample is the 20 fish caught. The population is all fish in the lake. The sample may be somewhat unrepresentative of the population since not all fish may be large enough to catch the bait.

**Example 2**: A college reports that the average age of their students is 28 years old. Is this a statistic or a parameter?

Answer: This is a parameter, since the college would have access to data on all students (the population)

### Try It

[ohm_question]6912[/ohm_question] [ohm_question]6910[/ohm_question]## Licenses & Attributions

### CC licensed content, Original

- Revision and Adaptation.
**Provided by:**Lumen Learning**License:**CC BY: Attribution.

### CC licensed content, Shared previously

- Populations and Samples.
**Authored by:**David Lippman.**Located at:**http://www.opentextbookstore.com/mathinsociety/.**License:**CC BY-SA: Attribution-ShareAlike. - Populations.
**Authored by:**Nils Dougan.**License:**CC BY-NC: Attribution-NonCommercial. - Population and sample.
**Authored by:**OCLPhase2's channel.**License:**CC BY: Attribution. - Question ID 6910, 33101.
**Authored by:**Lippman, David.**License:**CC BY: Attribution.**License terms:**IMathAS Community License CC-BY + GPL.