Notebook AtlasSURG0002 · Research methods: go to the course map

AtlasSession 3L7: Systematic errorsp.38–46, 82–85

Deviations from intended interventions

  1. Study designs primer
  2. What is systematic error
  3. Deviations from intended interventions

Fig. 1

Rat full-thickness skin wounds: growth-factor vs plain hydrogel, wound closure at day 14 (%)

Fig. 1. 24 rats per gel. Average wound closure 78% vs 64%.

Growth-factor gel: wound closure
78%
Plain gel: wound closure
64%
Extra care in one group?
no

Trial Design Board · First look

Daily re-dressing, plain gel re-dressing

Level 1 · First look · Lecture 7 · p.38–46, 82–85

See how extra care given to one group muddles a comparison.

Identify differential care or non-adherence as deviations from intended interventions, and judge the bias separately for the intention-to-treat (ITT) and per-protocol effects.

  1. Extra coaching (the step you are on)

    Two diets compared, but one group also gets a personal trainer. Which caused the weight loss?

    Two diets are compared, but one group also gets a personal trainer: which caused the weight loss? Here both gels get the same care: 78% vs 64% wound closure.

step 1/3