Allocation vs selection bias

[Phloston]

What is the difference between these two?

UWorld says allocation bias is merely the non-random allocation of participants into study groups, but I had always thought that was selection bias. In other words, is allocation bias merely a more specific type of selection bias? Or is there some more detail here?

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[tripwm]

Here's my best guess: Selection bias is used by some texts as an overhead term that would include categories such as sampling bias. Thus, they would use the term allocation as the bias for non random assignment. First Aid does, however, say selection bias is what this question defines as allocation bias. Perhaps a foreign test-writer complicating the issue?

 

[Phloston]

My concern is that UWorld lists allocation bias and selection bias as two separate answer choices for one of their questions.

So on the real USMLE, if non-randomization of study groups is discussed in a question, I wouldn't think it's wrong to put selection bias, even if allocation bias were an answer. That's why I'm asking about some sort of specific difference.

 

[tripwm]

My concern is that UWorld lists allocation bias and selection bias as two separate answer choices for one of their questions.

So on the real USMLE, if non-randomization of study groups is discussed in a question, I wouldn't think it's wrong to put selection bias, even if allocation bias were an answer. That's why I'm asking about some sort of specific difference.

Based on First Aid, the CA is selection bias. Based on some of my Behavioral Science lectures, selection bias is a category of bias whereas allocation bias is given the definition seen in First Aid. I would assume this is a case of 'which answer is more correct', which would be allocation bias.

Best you can do is hope the question doesn't appear. If it does, go with allocation bias.

 

[T3ddy]

Allocation bias is different from selection bias ; selection bias occurs when the selected sample doesn't represent the general population, random selection of the individuals can minimize this. Allocation bias occurs when there is a systematic difference between participants in how they are assigned to treatment groups this can be minimized by random allocation of patients to treatment groups randomization of already selected participants will not effect selection bias , so they are different

 

[pathologyDO]

Allocation bias is different from selection bias ; selection bias occurs when the selected sample doesn't represent the general population, random selection of the individuals can minimize this. Allocation bias occurs when there is a systematic difference between participants in how they are assigned to treatment groups this can be minimized by random allocation of patients to treatment groups randomization of already selected participants will not effect selection bias , so they are different

Not to be a downer but this thread is from 3 years ago

 

[Mkandil]

I guess selection bias is a sampling bias