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Chapter 1

Chapter 1: Research Methods

Chapter Review

Psychological claims are typically claims about facts, and to check on these empirical claims, psychologists rely on the methods of science.

MAKING OBSERVATIONS

  • Scientific observations typically begin with a question or hypothesis. The hypothesis must be specific enough to be testable, so that it will be clear what results might falsify the hypothesis. This requirement for testability usually calls for an operational definition of the key terms in the hypothesis, in order to specify the study’s dependent variable. The data for a study must also be systematically collected, and so researchers usually ignore anecdotal evidence.
  • Based on their observations of a sample, psychologists want to draw conclusions about a broad population. In random sampling, every member of the population has an equal chance of being picked to participate in the study. Researchers sometimes turn to other procedures, including case studies.
  • Often, researchers want their study to mirror the circumstances of the broader world; in this case, they need to ensure the study’s external validity. This validity depends on many factors, including the requirement that the study itself not change the behaviors the researchers hope to understand. One concern here involves the study’s possible demand characteristics— cues that can signal to the participants how they’re supposed to behave. One way of avoiding this problem is to use a double-blind design.

WORKING WITH DATA

  • Researchers use descriptive statistics to summarize the data from their studies. These include measures of central tendency of the data, often computed as the mean, and measures of the variability, often assessed by the standard deviation.
  • Researchers also use correlations to summarize the pattern of their data, asking whether changes in one measurement are somehow linked to changes in some other measurement. These linkages are often summarized via a correlation coefficient, r. Correlations can be used to check on the reliability of the measurements, and they’re also one way to assessing the measure’s validity.
  • Researchers use inferential statistics to make inferences based on their data. This process often involves testing a difference between two groups, and it typically provides an assessment of a result’s statistical significance—ultimately expressed as a p-value, the probability of getting the data pattern just by chance.

OBSERVATIONAL STUDIES

  • Observational studies are crucial for psychology, but they’re often uninformative about causation. In some observational studies, we can’t be sure which observation is the cause and which is the effect; in other cases, we need to worry about the third-variable problem—the idea that some other (i.e., third) variable is influencing both the variables observed in our study.

ESTABLISHING CAUSE AND EFFECT:

THE POWER OF EXPERIMENTS

  • To assess cause and effect, researchers typically turn to experiments in which they deliberately change some aspect of a situation and observe the results. It’s crucial for investigators to treat the experimental group and control group exactly the same in every way except for the experimental manipulation itself.
  • The two groups must also be matched at the outset of the experiment. In many cases, researchers use random assignment to ensure matching groups. In other cases, researchers use a within-subject comparison, although they must then take other precautions to address problems that might be created by the sequence of conditions in the procedure.
  • Scientific conclusions rarely rest on a single experiment. Instead, the experiment must be scrutinized by other researchers and usually replicated through subsequent studies. Only then can we confidently say that the original hypothesis has been confirmed or disconfirmed.

RESEARCH ETHICS

  • Researchers must take precautions to protect the study participants’ physical well-being as well as their privacy, autonomy, and dignity. If these ethical requirements collide with procedures needed to ensure a study’s validity, then all risks to the participants must be minimized. Any remaining risks must be fully justified on scientific grounds.

THE POWER OF SCIENCE

  • The methods of science can also be used to evaluate claims in everyday life. People can apply these methods to help ensure their conclusions are warranted. Relying on the methods of science can also help politicians make certain their policies are in line with the best available evidence.
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