AS Psychology Research Methods Research Processes, Variables, and Sampling

Hypothesis The aim tells the reader the researcher’s purpose of the study, and what it intends to show. A hypothesis, meanwhile, is a testable statement which predicts a difference between the levels of the IV in the experiment or a relationship between variables. The null hypothesis – there is no difference or relationship between variables. The alternate hypothesis – there will be a difference or relationship between variables.

Hypothesis (Cont’d) The non-directional (two-tailed) hypothesis does not predict the direction of the outcome. It simply states there will be a difference in the DV between levels of the IV. The directional (one-tailed) hypothesis predicts the direction in which the results will occur. The levels of the IV will produce an increase or a decrease in the DV.

Variables Operationalization – a generalized statement which defines the variables (IV and DV) so that they can be properly manipulated, measured, or quantified for replicating in the experiment. Control – a way of keeping possible extraneous variables constant to ensure measured differences in the DV are likely due to the IV and thus raising validity.

Variables (Cont’d) Strengths of Controlling Variables – more control over irrelevant/extraneous variables means that the DV is more likely to be due to the IV; cause and effect relationship is more likely to be shown. Participants are more likely to behave in predictable ways, particularly ways in which the experimenter wants them to behave. Weaknesses of Controlling Variables – controlling variables is reductionist since it's unlikely that any behavior would exist in isolation from others. Attempting to control variables for many different trials can lead to participants becoming suspicious (demand characteristics).

Variables (Cont’d) A pilot study is a small-scale trial run of the actual experiment. It allows the investigator to identify flaws of the experiment. A pilot study tests for problems with: - design of the experiment. - clarity of instructions for the participants. - measuring instruments. Also allows a time scale of the actual experiment to be estimated (longitudinal vs. snapshot).

Sampling A population is the group, sharing characteristics, from which the sample is drawn. A sample is the group of people (or animals) selected to represent the population in a study. Sampling technique is the method used to obtain the participants for a study from the population.

Sampling (Cont’d) An opportunity sample is selecting participants who are readily available and willing to take part. Strengths – easiest and cheapest method of recruitment. Weaknesses – unlikely to generate a representative sample of the target population so investigation could be offered to everyone at a school, for example, but then results couldn’t be generalized externally. A researcher might choose people they think look suitable, ignoring others, and so biasing the sample.

Sampling (Cont’d) A volunteer (self-selecting) sample is participants who are invited to participate through advertisements. Strengths – useful when the research requires participants of quite a specific type or with specific experience. It can be easy to place an advert in a newspaper. Weaknesses – volunteers are usually more stable and outgoing than those who do not (increased bias). More prone to demand characteristics. People may not see the advert or ignore it. We can never really be sure that a self-selecting sample is representative of the target population.

Sampling (Cont’d) A random sample is all members of the population who are selected in an unbiased method (names from a hat). Strengths – sample is likely to be representative so results can be generalized. High population validity. Weaknesses – researchers cannot force a person to participate so there is always some element of volunteering.