Sampling Methods

Question 1

What is sampling?

Answer 1

How we choose our participants

Question 2

Random sample

Answer 2

All members of the target population have an equal chance of being chosen.
Complete list of names of all members of population is obtained and the sample is selected randomly

Question 3

Systematic sample

Answer 3

Every nth member of the target population is chosen

Question 4

Stratified sample

Answer 4

Sample reflects proportions of people in certain subgroups.
Different strata that make up a population are identified.
Then the proportions of the strata are worked out.
Finally the participants that make up each stratum are selected using random sampling

Question 5

Opportunity sample

Answer 5

Researcher simply decides to select anyone who is willing and available

Question 6

Volunteer sample

Answer 6

Participants select themselves to be part of the sample, they volunteer

Question 7

Random sampling evaluation

Answer 7

• Unbiased as the researcher has no influence on who is selected - confounding and extraneous variables are controlled - enhances internal validity.
• Time-consuming and may not work - a complete list of the population is hard to get and some participants may refuse to take part. The sample may still be unrepresentative at the end

Question 8

Systematic sampling evaluation

Answer 8

• unbiased - the first item is usually selected at random - objective
• time and effort - a complete list of the population is required

Question 9

Stratified sampling

Answer 9

• avoids researcher bias and is more representative of a target population - it accurately reflects the composition of the population
• stratification isn’t perfect - identified strata can’t reflect all the ways that people are different so complete representation of the target population is impossible

Question 10

Opportunity sampling evaluation

Answer 10

• convenient and cheap - less time consuming
• unrepresentative of the target population and the researcher has complete control over the selection of the participants

Question 11

Volunteer sampling evaluation

Answer 11

• convenient and cheap - less time consuming
• may attract a certain type of person - will be unrepresentative of the population