Sampling (DM)

Question 1

DEFINITION
Target population

Answer 1

the people whose behaviour we are interested in

Question 2

DEFINITION
Sample

Answer 2

the people who are tested (participants)

Question 3

DEFINITION
Representative study

Answer 3

when the sample reflects the target population
(otherwise it is biased and not generalisable)

Question 4

DEFINITION
Biased sample

Answer 4

when the sample does not reflect the target population

Question 5

DEFINITION
Generalisable

Answer 5

the results from the sample can be assumed to apply to the target population

Question 6

DEFINITION
Sampling method

Answer 6

the technique used to select the sample

Question 7

Method:
Random sampling

Answer 7

everyone in the target population has an equal chance of being selected
e.g through a hat pull or number generator

+ve
-should be representative as there is no bias, the researcher has no control over who’s picked so the sample may be more generalisable
-extraneous variables are equally spread so greater internal validity

-ve
-may not always be possible or practical because it requires a full list of the target population
-increased time and effort in contacting the sample and some people may not want to participate anyway

Question 8

Method:
Stratified sampling

Answer 8

the target population is broken down into strata based on characteristics and a proportional amount from each group is randomly selected

+ve
-should produce a representative sample as the target pop. is broken into strata so findings can be generalised

-ve
-may not be practical or possible as it’s time consuming and complicated process, strata can be hard to define or may overlap

Question 9

Method:
Volunteer sampling

Answer 9

an advertisement is used so people in the target population can put themselves forward by responding to the advert

+ve
-the ONLY available method when a role is highly specialised

-ve
may produce a biased sample because volunteers are more likely to be keen, so sample is not representative so is not generalisable

Question 10

Method:
Systematic sampling

Answer 10

a structured way of selecting people from the target population
e.g selecting every 5th person on a register

+ve
-should produce a representative sample because participants are selected objectively (particularly if random method is used to select the 1st participant) so findings can be generalised

-ve
-may not always be possible or practical as it is time consuming as participants may refuse to take part and then the systematic flow is halted.

Question 11

Method:
Opportunity sampling

Answer 11

using whoever is available at the time and place of he study
ONLY usable when participants are unaware

+ve
-The only sampling method you can use when participants are unaware of the study

-ve
-may produce a biased sample as the sample is only drawn from a specific part of the target pop. so the findings cannot be generalised
-biased sample as researcher has complete control over selection

Question 12

Internal validity

Answer 12

The study’s results were truly caused by the variable being tested rather than by other outside factors.

Question 13

External validity

Answer 13

The extent to which the study’s findings can be generalized to other people, settings, and situations.