research methods and statistics psych chunk 3

Research Methods

• Descriptive research → case studies, surveys, observation

  • Pro: gives natural information, good starting point

  • Con: cannot show cause-and-effect

• Correlational research → looks at relationships between variables

  • Pro: helps make predictions

  • Con: does not prove cause-and-effect

• Experimental research → researcher changes one variable (independent variable) and measures the effect on another (dependent variable)

  • Pro: strongest evidence for cause-and-effect

  • Con: may not reflect real life perfectly

Key Terms

• Operational definition = clear definition of how a variable is measured

• Population = the whole group you want to study

• Sample = the smaller group you actually study

• Random assignment = gives each participant an equal chance, reduces bias

• Reliability = results are consistent

• Validity = results are accurate (measuring what you intend to measure)

Statistics

Measures of Central Tendency

• Mean = the average score

• Median = the middle score

• Mode = the most common score

Spread of Data

• Range = difference between highest and lowest score

• Outlier = score much higher or lower than the others

• Standard deviation (SD) = shows how spread out the scores are

  • Small SD = scores are close together

  • Large SD = scores are spread apart

Scatterplots (types of relationships)

• Positive relationship = as one goes up, the other goes up

• Negative relationship = as one goes up, the other goes down

• Curvilinear relationship = changes direction at some point

• No relationship = no pattern in the data

Pearson’s r

• +1 = perfect positive

• −1 = perfect negative

• 0 = no relationship