Lesson 6 Sampling Techniques and Pilot Study

Question 1

Target Population

Answer 1

This describes the group who researchers are studying and want to generalise their results to. For example the target population might be all females aged 20-30 that shop online.

Sampling techniques are used to obtain a sample of the target population and are essential to avoid studying entire populations, which would take too long and be too expensive.

Question 2

Sample

Answer 2

A sample should be representative of the population from which it is drawn and should therefore have the same characteristics as the population. E.g. if the female target population aged 20-30 consists of different social classes and ethnicities, then the sample should reflect this too.

Question 3

Random Sampling

Answer 3

Random sampling is when every member of the target population has the same chance of being selected. The easiest way to do this is to place all names from the target population in a hat e.g. 100 possible participants from the sixth form that study psychology and Maths. We then select our sample, e.g. the first 20 participants’ names that are drawn from the hat.

Question 4

Advantages of Random Sampling

Answer 4

1) If the target population is large and a large sample is drawn, then it is likely the sample will be representative and therefore results can be generalised from the sample to the target population.

2) There is no researcher bias when selecting the sample, this is because the sample have been chosen by chance without any conscious choice from the researcher. Everyone has an equal chance of being selected.

Question 5

Disadvantages of Random Sampling

Answer 5

1) It is sometimes difficult to get full details of a target population from which to select a sample. An example might be that it is not possible to get a full list of all of the women aged 20-30 in the UK as some women might not appear on the list due to being in prison, not being registered etc.

2) Not all members of the target population who are selected to take part will be available or willing to take part, making the sample unreliable Some people might refuse to take part in a study. This could reduce your sample size dramatically too.

Question 6

Systematic Sampling

Answer 6

Systematic sampling is a sampling strategy where participants are selected by taking every Nth person from a list. So for example, make a list of the total population of the sixth form that you wish to study, and then select every 6th person on the list. These people become your sample.

Question 7

Advantages of Systematic Sampling

Answer 7

Systematic sampling is far more simple than random sampling as it only requires a list of the target population, and then the researcher decides to select every nth person. Random sampling requires a lot more time and effort (gain the list of the target population, put all of the individual names on bits of paper, and then randomly select a number of people to form the sample)

Question 8

Disadvantages of Systematic Sampling

Answer 8

1) The process of selection can interact with a hidden periodic trait within the population. If the sampling technique coincides with the periodicity of the trait, the sampling technique will no longer be random

2) Not all members of the target population who are selected to take part will be available or willing to take part, making the sample unrepresentative. Some people might refuse to take part in a study. This could reduce your sample size dramatically too.

Question 9

Stratified Sampling

Answer 9

Stratified sampling involves classifying the population into categories and then randomly choosing a sample which consists of participants from each category in the same proportions as they are in the population.

The population are divided into strata in terms of characteristics e.g. age, gender etc. A sample is then selected that reflects these characteristics, e.g. 51% female and 49% male. Data about the sample in the UK can be gained from the Census. Stratified samples can ensure that the sample is representative.

Question 10

Advantages of Stratified Sampling

Answer 10

The strength of stratified sampling is that all groups within a population are included, therefore the sample should be representative of the population.

Question 11

Disadvantages of Stratified Sampling

Answer 11

Stratified sampling can be very time consuming as the categories have to be identified and calculated. If you do not have details of all the people in your target population or the relevant strata, you would struggle to conduct a stratified sample.

Question 12

Opportunity Sampling

Answer 12

Opportunity sampling involves selecting participants who are readily available and willing to take part.

This is sometimes known as convenience sampling. This involves selecting participants simply because it is convenient to do so. Psychologists might have easy access to a group of people that they know well or have regular contact with. It might therefore be convenient to approach these people to ask them to take part in their research

Question 13

Advantages of Opportunity Sampling

Answer 13

This is the easiest and most practical method of ensuring large samples especially when compared to stratified sampling which might be very time consuming and expensive to carry out.

Question 14

Disadvantages of Opportunity Sampling

Answer 14

There is a high chance that the sample will not be representative of the target population. Sometimes people feel obliged to take part in research (especially if someone they know is conducting the research, they might find it hard to say no) even when they do not really want to, this is unethical

Question 15

Volunteer Sampling

Answer 15

Volunteer sampling involves people volunteering to participate in a study. The researcher will usually ask for people to take part in their research. Researchers can advertise by using leaflets, posters, radio or TV broadcasts. These forms of communication means that people take notice of the information and can then decide if they would like to take part in the research and volunteer their time.

Question 16

Advantages of Volunteer Sampling

Answer 16

This method saves the researcher time and effort. The researcher needs to construct some kind of advertisement for the study and then just needs to wait for the participants to come to them to volunteer their time and involvement. This is better than other sampling methods where the researcher needs to ask people to take part and needs their full commitment.

Question 17

Disadvantages of Volunteer Sampling

Answer 17

A certain type of person tends to volunteer (enthusiastic, interested in your topic) and this means that there is a very high chance that the sample obtained will be unrepresentative and will not accurately reflect the target population (volunteer bias).

Question 18

Pilot Study

Answer 18

• A pilot study is an initial run-through of the procedures to be used in an investigation; it involves selecting a few people and trying out the study on them. It is possible to save time, and in some cases, money, by identifying any flaws in the procedures designed by the researcher.
• A pilot study can help the researcher spot any ambiguities (i.e. unusual things) or confusion in the information given to participants or problems with the task devised.
• Sometimes the task is too hard, and the researcher may get a floor effect, because none of the participants can score at all or can complete the task – all performances are low. The opposite effect is a ceiling effect, when the task is so easy that all achieve virtually full marks or top performances and are “hitting the ceiling”.

Question 19

When using self-report it is important to check as part of the pilot study

Answer 19

· The participants understand the questions and are prepared to answer them

· That closed questions offer suitable options

· Whether open questions are also needed to elicit unpredictable responses

· Whether the reporting method is appropriate, e.g. if a face-to-face interview is too intimidating should it be changed to a questionnaire?

Question 20

In observations it is important to check

Answer 20

· Observers agree on operational definitions of behavioural categories

· Inter-observer reliability – do the researchers need practice observing the behaviours?

· The behavioural categories include all the important behaviours

· The behavioural categories do not overlap

· Whether the participants are affected by the observers – should they be covert?

Question 21

Advantages of Pilot Study

Answer 21

You can make changes and modify the main study

Question 22

Disadvantages of Pilot Study

Answer 22

Can be very time consuming and expensive