Research Design Issues in Health Sciences - Week 3 Part 2

Researcher control in surveys

Variables are not under the researcher's direct control.

Purpose of surveys in the real world

To examine naturally occurring patterns.

What do surveys determine between variables?

The correlation between variables of interest.

Variables measured in surveys

Both Independent Variables and Dependent Variables.

Internal vs. External Validity Trade-off

Increasing internal validity through tight control often decreases external validity.

Ecologically Valid Approaches

Using real-world conditions like field experiments or 'living labs'.

Blinding

Hiding information about the study from people involved.

Single-blind study

Study where the participant doesn't know their treatment group.

Double-blind study

Study where both participants and researchers are unaware of treatment groups.

Purpose of blinding

Helps prevent a range of potential experimenter biases and effects.

Best practice for blinding

Use it if possible and describe exactly who and how you did so.

Confounds

Changes in your DV (outcome variable) due to another variable, NOT your IV (treatment variable).

Maturation Effects

Natural changes over time, such as children's physical and cognitive development, that can be confused with the effect of the treatment.

History Effects

External events occurring in the world between pre- and post-test (e.g., COVID-19, 9-11) that can affect study outcomes.

Testing effects

Reflect the situation where for one reason or another the original testing situation affects the subsequent testing situation.

Delays between pre- and post-test

Even short delays can cause problems in the form of practice effects and fatigue effects.

Reactivity

When something about the study itself means only particular people respond or influence how people respond.

Mortality in studies

When people drop out from a study, which can also affect external validity.