i'm looking for the statistical term or description for a type of bias:
Let's say there's an exam which most pupils pass easily, eg 80% pass-rate on first attempt
At one poorly performing school the pass-rate is very bad eg only 20%
These pupils have to take the exam several times before passing, eg 4 or 5 times.
Now this school is saying that the "average" pass-rate is 50% approx.
This is clearly misleading, because it is they who bring the average down, and in any case, a pupil from another school can reasonably expect to have a better chance than 50%...
Is there a name to this sort of biased statistical reporting?? thanks!!
Let's say there's an exam which most pupils pass easily, eg 80% pass-rate on first attempt
At one poorly performing school the pass-rate is very bad eg only 20%
These pupils have to take the exam several times before passing, eg 4 or 5 times.
Now this school is saying that the "average" pass-rate is 50% approx.
This is clearly misleading, because it is they who bring the average down, and in any case, a pupil from another school can reasonably expect to have a better chance than 50%...
Is there a name to this sort of biased statistical reporting?? thanks!!