AtlasSession 3L7: Systematic errorsp.9–12, 72–73
What is systematic error
- Study designs primer
- What is systematic error
- Next: Confounding
Fig. 1
Compressive modulus of hydrogels A and B, both truly 45 kPa; A tested on a rig with an uncorrected pre-load (kPa)
Fig. 1: hydrogel A and hydrogel B are equally stiff (45 kPa, the dashed line). Hydrogel A stands on a box: its rig adds 4.0 kPa of pre-load. Hydrogel A looks stiffer, by about 4 kPa.
- Real difference
- none: equally stiff
- Looks stiffer
- hydrogel A
- By about
- 4 kPa
- Box
- under hydrogel A
Agreement & Error Lab · First look
Level 1 · First look · Lecture 7 · p.9–12, 72–73
Explain bias as a built-in tilt from how a study is done.
Define systematic error (bias, internal validity) as a deviation from truth caused by how research is done, and list the 7 ROBINS-I domains.
Standing on a box (the step you are on)
Two people of equal height; one stands on a box and says 'I am taller' (p.10).
Two people of the same height: the one standing on a box says ‘I am taller than you!’ (p.10). Here the box is under hydrogel A.