Sampling technique and research designs

What is the sampling technique?

What is the relationship between a sample and a population?

• A sample is a group that is representative of the larger pool of people from which it is drawn.

• Samples always come from the researcher's culture; populations are global.

• A sample is the participants that are taken from a group to which you want to generalize the results of the study.

• Samples are all the people possible for a study; the population is the participants that actually show up.

In convenience sampling, the sample is based on the convenience of the researcher, using whatever population happens to be available, and focusing the study on that population's relevant characteristics. This sampling technique is considered:

• Probability sampling

• Non-probability sampling

What is one disadvantage of convenience sampling?

Why don't we use random sampling?

• It is the most labour-intensive sampling technique, because it first requires the identification of relevant subgroups within a population and then simple random samples from each subgroup

• It tends to over-represent whichever subgroups in the target population happen to be most readily available.

• It tends to over-represent whichever subgroups in the target population happen to be most readily available.

• It is not really possible for our psychological research, because every member of a target population is not really identifiable or accessible.

What is the research design?

This research design uses two separate groups of participants, and each participant is tested in only one condition of the experiment. 

• Independent measures design

• Repeated measures design

• Matched pairs design

Independent measures designs have the problem of participant variability. What does this mean?

• Participants tend to drop out of the study because of boredom.

• Participants have different levels of skill, so some understand the instructions better than others.

• Participants are not the same as the general population and the results cannot be generalized.

• Differences in the traits and past experiences of the participants in each condition may affect the results of the study.

This research design uses the same participants in all conditions of an experiment.

• Independent measures design

• Repeated measures design

• Matched pairs design

Which of the following is not true of a repeated measures design?

• Fewer participants are needed than for an independent samples design.

• Participants are less likely to show demand characteristics than in an independent samples design.

• Participants are more likely to show order effects - such as improvement of a skill through practice - than in an independent samples design.

• Participant variables are controlled.