Lecture 5

Question 1

Population

Answer 1

the entire set of elements (individuals or other entities!) from which the sample is to be selected (and to which the study findings are to be generalized

Question 2

Sample

Answer 2

the segment of population that is selected for investigation

Question 3

Generalizability

Answer 3

• Can the findings from a sampling of the population be generalized to the population from which the sample was selected
• Can the findings from a study of one population be generalized to another, somewhat different population?

Question 4

Random sample

Answer 4

each element has an equal probability of selection

Question 5

Sampling frame

Answer 5

A list of all the elements in a population

Question 6

Census

Answer 6

A study of all members of a population

Question 7

Representative sample

Answer 7

a sample that reflects the population accurately

Question 8

Probability sample

Answer 8

sample selected using random selection

Question 9

Non-probability sample

Answer 9

sample selected without using a random selection method

Question 10

Sampling error

Answer 10

Any difference between the characteristics of the sample and the characteristics of the population. Note that sampling error occurs even with a probability sampling method

Question 11

Absolute size matters

Answer 11

As sample size increases, sampling error decreases

Question 12

heterogeneity

Answer 12

The greater the heterogeneity of the population the larger a sample will need to be.

Question 13

Sampling bias (or systematic bias)

Answer 13

A distortion in the representativeness of the sample that arises when some members of the population stand less chance of being included in the sample

Question 14

Non-response

Answer 14

Non-sampling error that occurs when people refuse to cooperate, cannot be contacted, or have other reasons why they cannot supply data

Question 15

Attrition

Answer 15

Sample gets smaller in number because participants drop-out of the study for various reasons

Question 16

Systematic sampling

Answer 16

From a random starting point, choose every nth unit

Question 17

(Proportionate) stratified sampling

Answer 17

Each sample is taken as a proportional representation from its stratum.

Question 18

Quota sampling

Answer 18

Elements are selected to ensure that the sample represents certain characteristics in proportion to their prevalence in the population

Question 19

Purposive sampling

Answer 19

• Each sample element is selected for a purpose.
• Researchers may look for subjects with certain characteristics, because these characteristics are relevant to the research question

Question 20

Snowball sampling

Answer 20

Sample elements are identified by informants or interviewees

Question 21

Convenience sample

Answer 21

In a convenience sample (or availability sample), the researcher simply uses what he/she can get

Question 22

Matching

Answer 22

Match subjects across different samples on certain characteristics

Question 23

When do you need a representative sample?

Answer 23

When the research explicitly aims to generalize its findings to a real-world population