Problems with Correlational Research

Directionality Problem
– A problem encountered in correlational studies; the
researchers find a relationship between two variables, but they cannot
determine which variable may have caused changes in the other variable.
Third Variable Problem
– A problem that occurs when the researcher cannot
directly manipulate variables; as a result, the researcher cannot be confident
that another, unmeasured variable is not the actual cause of differences in the
variables of interest.
Components of Experimental Research
•
Independent variable
- The variable that gets manipulated
Dependent variable
- The variable that gets measured. “depends” on the
independent variable
•
Experimental group
– Treatment groups; the participants in a study that
receive the intervention.
•
Control group
– A comparison group; the participants in a study that receive
no intervention or receive an intervention that is unrelated to the
independent variable being investigated.
Problems with Experimental Research
•
Confounds
- Anything that affects a dependent variable and may
unintentionally vary between the experimental conditions of a study.
•
Sample
– A subset of a population.
•
Selection bias
- In an experiment, unintended differences between the
participants in different groups.
–
How to correct sample issues?
•
Random samples
•
Random assignment
- Placing research participants into the
conditions of an experiment in such a way that each participant
has an equal chance of being assigned to any level of the
independent variable.
Good Research Requires
•
Construct validity
– The extent to which variables measure what they are
supposed to measure.
•
External validity
– The degree to which the findings of an experiment can be
generalized outside the laboratory.
•
Internal validity
– The extent to which the data collected in a study address
the research hypothesis in the way intended.
•
Reliability
– The extent to which a measure is stable and consistent over time
in similar conditions.
•
Accuracy
– The extent to which an experimental measure is free from error.
Analyzing Data
•
Descriptive statistics:
–
Measures of central tendency
•
Mean
– A measure of central tendency that is the arithmetic
average of a set of numbers.
•
Median
– A measure of central tendency that is the value in a
set of numbers that falls exactly halfway between the lowest