Epi W2 Bias

What is study validity?

What is study validity?

The validity of a research study refers to how well the results among the study participants represent true findings among similar individuals outside the study. Do the study results reflect the truth?

What are the two types of validity?

• Internal

• External

What is internal validity?

The extent to which the observed results represent the truth in the population we are studying and, thus, are not due to methodological errors.

Give 3 examples of threats to the internal validity of a study.

• Chance

• Bias

• Confounding

Make two pairs out of these 4 words:

• Validity

• Reliability

• Accuracy

• Precision

• Validity and accuracy

• Reliability and precision

Which threat to internal validity affects the precision of the results?

Chance

Which threat to internal validity affects the accuracy of the results?

Bias

What is the alternative explanation or threat to internal validity that is neither chance nor bias?

Confounding

What is external validity?

The extent to which the results of a study are generalisable to patients in daily practice, especially for the population that the sample is thought to represent, or to other populations/settings.

What is the difference between internal and external validity?

What are the two types of error in epidemiological studies?

• Random error

• Systematic error

Describe the precision and accuracy of these results.

Low precision: scattered across different levels.

Low accuracy: not reflecting the truth.

Describe the precision and accuracy of these results.

High precision: data points close together, low variability

Low accuracy: not reflecting the truth

Describe the precision and accuracy of these results.

Low precision: data points scattered.

High accuracy: reflecting the truth.

Describe the precision and accuracy of these results.

High precision: data points close together

High accuracy: reflecting the truth

What are sources of random error?

• Individual/subject

• Observer

• Machine

What are sources of systematic error?

• Observer

• Machine