PSYCH109 - RESEARCH METHODS 30 KEY POINTS

What are the three key principles of scientific research identified by Merton?

Communality — scientific knowledge should be shared; universalism — claims should be evaluated independently of who made them; organised scepticism — scientific claims should be critically evaluated rather than accepted automatically.

What is the difference between a hypothesis and a theory?

A hypothesis is a specific, testable prediction, while a theory is a broader explanation supported by evidence that can generate multiple hypotheses.

What is an independent variable (IV)?

The variable that is manipulated or systematically varied by the researcher to examine its effect on another variable.

What is a dependent variable (DV)?

he variable that is measured as the outcome of a study. It is what the researcher is interested in explaining or predicting.

Why is identifying the dependent variable important when evaluating sampling bias?

A biased sample is only a problem if the characteristics causing the bias are related to the DV. A sample can be unrepresentative in one respect but still appropriate for studying a particular outcome.

What is sampling bias?

Sampling bias occurs when a sample systematically misrepresents the population, making some groups or characteristics more likely to be included than others.

What is the difference between correlation and causation?

Correlation means two variables are related, but it does not establish that one causes the other. Causation requires evidence that changes in one variable produce changes in another.

What are the three possible explanations for a correlation between two variables?

A causes B, B causes A, or a third variable causes both A and B.

Why can't a correlational study establish causation?

Researchers do not control or manipulate the variables, so they cannot rule out reverse causation or third-variable explanations.

What is an experiment?

A study in which researchers manipulate an independent variable and measure its effect on a dependent variable, allowing stronger conclusions about causation.

What makes a study better suited to testing causation?

Manipulation of the IV, measurement of the DV, and control of potential confounding variables, ideally through random assignment.

What is random assignment?

Randomly placing participants into different experimental conditions so that pre-existing differences between groups are less likely to systematically affect the results.

What is a confounding variable?

An uncontrolled variable that differs between conditions and could provide an alternative explanation for the observed effect.

What did the Stroop effect demonstrate?

People are slower and make more errors when naming the ink colour of an incongruent colour word (e.g., the word “BLUE” printed in red), demonstrating interference between automatic and controlled processes.

What is statistical significance?

A result is statistically significant when it would be unlikely to occur under the null hypothesis, according to a chosen significance criterion such as p < .05.

What is the null hypothesis?

The hypothesis that there is no effect, difference, or relationship in the population being studied.

What is the alternative hypothesis?

The hypothesis that there is an effect, difference, or relationship in the population.

What is a Type I error?

Rejecting a true null hypothesis — concluding that an effect exists when it actually does not. This is a false positive.

What is a Type II error?

Failing to reject a false null hypothesis — concluding that there is not enough evidence for an effect when one actually exists. This is a false negative.

What is the difference between a one-tailed and two-tailed hypothesis test?

A one-tailed test predicts the direction of an effect (e.g., A will be greater than B), while a two-tailed test predicts only that the groups will differ, without specifying the direction.

What is Merton's principle of communality?

Scientific knowledge should be treated as shared knowledge, rather than belonging exclusively to the individual researcher who discovered it.

What does universalism mean in science?

Scientific claims should be evaluated based on evidence and scientific criteria, not on the identity, status, nationality, or reputation of the person making the claim.

What does organised scepticism mean?

Scientific claims should be critically examined and questioned, rather than accepted simply because they come from an authority or previous research.

Why is replication important in scientific research?

Replication helps determine whether a finding is reliable and reproducible, rather than being the result of chance, methodological problems, or an unusual sample.

Why does sample size matter in research?

Larger samples generally provide more precise estimates and reduce the influence of unusual individuals, although a large sample does not automatically eliminate sampling bias.

Why doesn't a representative sample need to match the population on every characteristic?

It only needs to be appropriate for the dependent variable being studied. A characteristic that differs between the sample and population may not matter if it doesn't affect the outcome of interest.

Why might recruiting undergraduate psychology students be problematic for some research questions but not others?

Psychology students may differ from the general population in important ways. This matters when those differences are related to the DV, but may matter much less when studying characteristics unrelated to those differences.

What is the difference between an observational and an experimental study?

In an observational study, researchers measure naturally occurring variables without manipulating them. In an experiment, researchers manipulate an IV to test its causal effect on a DV.

What does the example of self-esteem and intelligence demonstrate about correlation?

Even if self-esteem and intelligence are correlated, the relationship alone cannot show that self-esteem causes intelligence or intelligence causes self-esteem. Other variables could explain the relationship.

What does the “fake IQ test” example demonstrate about experimental research?

Manipulating participants' beliefs about their intelligence can allow researchers to test whether those beliefs cause changes in behaviour or performance, illustrating why experimental manipulation is useful for establishing causation.