Selecting Research Participants

Question 1

What is the difference between a sample and a population?

Answer 1

Sample - a set of individuals selected from a population meant to represent a population
Population - the entire set of individuals of interest to the researchers

Question 2

What is a target population?

Answer 2

A group defined by a researcher’s specific interests

Question 3

Why might target populations not be easily accessible?

Answer 3

The researcher may not have access to most people that are able and willing to be recruited for the study

Question 4

What is an accessible population?

Answer 4

An easily accessible segment of the target population which most researchers use to select a sample from

Question 5

What is the extent to which the characteristics of a sample accurately reflect the characteristics of a population called?

Answer 5

Representiveness

Question 6

To generalize the results of a study to a population, what would a researcher need to select?

Answer 6

A representative sample

Question 7

What is the most major threat to selecting a representative sample?

Answer 7

Bias - a biased sample has noticeable different characteristics from the population.

Question 8

What is the type of bias where individuals are selected in a manner that increases the possibility of obtaining a biased sample?

Answer 8

Selection bias (aka sample bias)

Question 9

In the field of statistics, what is the principle of the law of large numbers?

Answer 9

The larger the sample size, the more accurate the values are to the population

Question 10

What is the process of selecting individuals for a study called?

Answer 10

Sampling

Question 11

Sampling methods fall under two basic categories. What are they?

Answer 11

1. Probability sampling
2. Nonprobability sampling

Question 12

What are the 3 conditions of probability sampling?

Answer 12

1. Exact size of the population must be known
2. Each individual must have a specified probability of selection
3. Selection must be a random process and each individual has an equal chance of being chosen

Question 13

In nonprobability sampling, the population and individual probabilities are not completely known. How does the sampling method base itself on to reduce bias?

Answer 13

Based on factors like common-sense or ease, effort towards representativeness

Question 14

What type of sampling is the starting point for most probability sampling techniques?

Answer 14

Simple random sampling

Question 15

What are the 3 steps of simple random sampling?

Answer 15

1. Clearly define the population from which a sample will be chosen from
2. List all members of the population
3. Use a random process to select individuals from the list

Question 16

What are the 2 principal method of random sampling and how do they work?

Answer 16

1. Sampling with replacement - an individual selected returns to the population after being recorded, so that the odds of being chosen are consistent throughout selection, ensuring independent selections
2. Sampling without replacement - and individual selected is removed from the population, changing the odds of being chosen throughout selections, and independent selections are not produced

Question 17

What is a concern about simple random sampling?

Answer 17

Because chance determines each selection, it is possible, albeit unlikely, to obtain a distorted and non-representative sample

Question 18

What is systematic sampling?

Answer 18

Similar to simple random sampling, obtaining a sample by selecting every nth participant from a list containing the total population

Question 19

Why is systematic sampling less random than simple random sampling?

Answer 19

The principle of independence is violated

Question 20

What is stratified random sampling?

Answer 20

A sampling technique that identifies specific subgroups to be included into the sample, then selecting equal-sized random samples from those specific subgroups to make up a sample

Question 21

Why isn’t stratified random sampling considered totally random?

Answer 21

All individuals in the population are not equally likely to be selected, as the subgroup sizes are often different in size

Question 22

What is proportionate (stratified) random sampling?

Answer 22

A sampling technique that identifies specific subgroups and proportionately selects from them to make up a sample

Question 23

What is cluster sampling?

Answer 23

A sampling technique that involves random groups as opposed to random individuals from a population

Question 23

Why is convenience sampling considered weak?

Answer 23

It does not require knowledge of the population nor does it use a random process for selection, therefore the individuals are unlikely to be representative of the population

Question 23

What is the most commonly used sampling in behavioural science and how does it work?

Answer 23

Convenience sampling - researchers simply select individuals who are able and willing to respond, as they are easy to get

Question 24

What 2 strategies do researchers use to strengthen the flawed practice of convenience sampling?

Answer 24

1. Attempt to ensure samples are reasonably representative and not strongly biased
2. Provide a clear description of how the sample was obtained and who the participants were

Question 25

What nonprobability sampling method involves identifying specific subgroups to be included in the sample and then establish quotas for individuals to be sampled from each group?

Answer 25

Quota sampling

Question 26

If a researcher does not know the entire list of people in a population, and wants to represent equally sized groups in a sample, what method should be used?

Answer 26

Quota sampling