Lesson 3 - Sampling techniques

Question 1

Sampling is the process of….

Answer 1

selecting participants for a study

*sampling is key. Bad sampling can break a study

Question 2

Sampling began in the…. with…

Answer 2

1800s with political polling and marketing

Question 3

Researchers want to ensure that their samples are …..

Answer 3

good representations of the populations they want to study

Question 4

The goal of research is to….

Answer 4

generalize from the sample to the entire population

Question 5

What is the difference between the target and the accessible population

Answer 5

Target - group defined by the researcher’s specific interests

Accessible - the people the researcher can realistically involve in the study

Question 6

How well one can generalize the results from a given sample to the population depends on…..

Therefore, the researcher must determine….

Answer 6

• the samples representativeness
• how well the sample represents the target population

Question 7

Describe selection bias

Answer 7

Participants or subjects are selected in a manner that increases
the probability of obtaining a biased sample.

• not always conscious - might be ignorance or subconscious bias

Question 8

Accuracy of a sample improves rapidly as….

Answer 8

the sample size increases

Question 9

Outline 3 requirements for Probability sampling

Answer 9

*The exact size of the population must
be known, and it must be possible to list all the individuals.
* Each individual in the population must have a specified probability of selection.
* The selection process must be
unbiased; must be a random process

Question 10

In non-prob sampling, the odds of selecting a particular individual are…

Answer 10

unknown

Question 11

A good way of telling is a sample is representative of a population is if the sample is….

Answer 11

normally distributed

*why psych often avoids dichotomous formats

Question 12

The basic principle of probability sampling is that:

Answer 12

A sample will be representative if
all members of the population have an equal chance of being selected

*only needs to be representative in characteristics relevant to the study

Question 13

List the 5 types of probability sampling and their weaknesses

Answer 13

1. Simple random - fair and unbiased, but no guarantee that the sample is representative
2. Systematic - selections not random or independent
3. Stratified random - each subgroup has representation, but overall sample may not represent the population
4. Proportionate stratified - solves weakness of stratified, but some strata may have limited representation in the sample
5. Cluster - selections not random or independent

• can use a combined sampling strategy

Question 14

What the 4 types of non-prob sampling

Answer 14

Convenience sampling
Quota sampling
Purposive/Judgemental sampling
Snowball sampling

Question 15

Outline convenience sampling

Answer 15

• indis selected from those who are available and willing
• easy but a weak form of sampling as it is likely biased

Question 16

Outline snowball sampling

Answer 16

• used in exploratory research when participants are hard to find
• mostly vulnerable groups
• data collected from a few memebers of pop, found through referrals

Question 17

Outline purposive/judgmental sampling

Answer 17

• select participants on the basis of knowledge
• done for a particular subset of a population

Question 18

Outline quota sampling

Answer 18

• Subgroups identified to be included; quotas established for individuals to be selected through convenience from each subgroup
• researcher is able to control the composition of a convenience sample
• addresses issue of representativeness (though sample is therefore probably biased)

Question 19

Give 2 ethical principles in selecting participants

Answer 19

• select in a non-discriminatory manner (which probability sampling is ideal)
• use data from all participants selected

Question 20

One issue with research at large is that…

Answer 20

there is a strong bias towards publishing data from WEIRD populations - due to habitual dependence on convenience sampling