Data Collection

What is a population?

A whole set of items or people of interest

What is a sample?

Subset of a population that represents the population

What is a sampling frame?

Individual units of population

What is a sampling frame?

List of sampling units

What is a census?

Data collected from the entire population

What are the advantages of a census?

• More accurate results

What are the disadvantages of a census?

• Hard to manage data

• Time-consuming

What are the advantages of samples?

• Cheap

• Less data to process

What are the disadvantages of a sample?

• Less accurate

• Not representative

What are the three types of random sampling?

• Simple

• Systematic

• Stratified

How do you carry out simple random sampling?

• Need sampling frame

• Each item given a specific number

• Use a random number generator to select items

What are the advantages of simple random sampling?

• No bias

• Cheap

What are the disadvantages of simple random sampling?

• Sampling frame needed

• Not suitable for large samples

What is systematic sampling?

Samples chosen at regular intervals in an ordered list.

What are the advantages of systematic sampling?

• Easy to use

• Suitable for large populations

What are the disadvantages of systematic sampling?

• Sampling frame is needed

• Bias if sampling frame not random

What is stratified sampling?

The population is divided into strata (groups) and a simple random sample is carried out in each group.

What are the advantages of stratified sampling?

• Data is proportionally represented

What are the disadvantages of stratified sampling?

• Time consuming placing population into strata

What is quota sampling?

• Researcher selects sample that is representative of whole population

What are the advantages of quota sampling?

• No sampling frame needed

• Cheap

What are the disadvantages of quota sampling?

Bias

What is opportunity sampling?

• Researcher takes observations at time of study

What are the advantages of opportunity sampling?

• Cheap

• Easy to do

What are the disadvantages of opportunity sampling?

Non-representative result

What is discrete data?

Data measured at specific values

What is continuous data?

Data that can take any value in a given range