{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

14 Experimental design - Goals of experiments Eliminate...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Goals of experiments ! Eliminate bias ! Reduce sampling error (increase precision and power) Design features that reduce bias ! Controls ! Random assignment to treatments ! Blinding Controls ! A group which is identical to the experimental treatment in all respects aside from the treatment itself. Example: placebo ! Some illnesses, e.g. pain and depression, respond to fact of treatment, even with no pharmaceutically active ingredients ! Control: "sugar pills"
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Example: independent recovery ! Patients tend to seek treatment when they feel very bad ! As a result, they often visit the doctor when they are at their worst. Improvement may be inevitable, even without treatment ! Therefore, we need a control, untreated group to compare with, if we want to measure the effects of a new therapy Random assignment averages out the effects of confounding variables Experiment: individuals are randomly assigned to treatments
Background image of page 2
Background image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}