6 ms·
The potential for systematic bias here is also quite concerning. Imagine your experimental group tends to come in the morning (maybe because they're on-site) bu
by gwern 3y ago
The potential for systematic bias here is also quite concerning. Imagine your experimental group tends to come in the morning (maybe because they're on-site) but your control group is scheduled to come in the rest of the day...
- deleted 3y ago[deleted]
- biomcgary 3y agoThis problem is VERY real and happens in surprising ways. My biotech has a dataset that was collected over several years and we found this pattern of older people having more Vitamin D in their blood than younger people, which is the opposite of the published literature. It turns out that the sample collection was initially year round but switched to summer only and everyone in the cohort was older, by definition, in the later collection.