For example if there is any statement like:

Genetic drift occur due to change in gene pool by chance. It could be due to bottle neck effect, founder effect or migration.

I know that most of the time genetic drift occur due to bottle neck effect or founder effect. Migration can also cause it but most of the time it happen due to other factors.

So if in exam a True/False question came as follows:

Genetic drift is caused by migration. True/False

Then what should I do as I know that it could occur due to migration but some other factors are more prevalent.

How could I know what is inside examinar's head?

I don't know if this forum is correct place to ask exam like questions but I found it has 'Exam' tag so I asked it.

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    We can't know what's inside the examiners head either. Such questions should optimally asked in such a way that there is an unambiguougs solution. If there isn't, the question is not good. Sep 24, 2023 at 15:01

4 Answers 4


Ask the invigilator. If that's not possible, put your best guess and get ready to defend your answer

Genetic drift is caused by migration. True/False

Answer with "True". If the correct answer turns out to be False, be ready to argue why True should also be acceptable. This is better than answering with "False", since strictly speaking, a "False" answer here implies that genetic drift is not caused by migration, which as you've said is not the case.

See also this question.


The proper answer would be True, since it doesn't ask if that is the only cause. But, you might have to argue that point with the professor and you might not win such an argument if they are overly rigid. But to answer False seems to be much harder to justify.

If you get marked down and also get pushback, then you might want to have a few other students join the argument with you.

A better phrasing of the question that would remove the possible ambiguity would be either

Genetic drift is caused only by migration. True/False


Genetic drift is possibly caused by migration. True/False

Since True/False answers don't admit ambiguity, neither should the questions.


The best approach to hypothesis testing is as such: Are there any cases where the posted statement is absolutely not true? If so, the proposition being made is false.

A true/false question on an exam might to first order be answered properly with the same approach.

Certainly, the validity in the above approach is based on a foundation that any proposition posted for yes/no validation is well-framed. An example of an ill-framed proposition relevant for your case is one that leaves some aspects of the exact cause-effect relationship that is being posited as ambiguous.

Pushing the original statement as true is somewhat as though you are agreeing to the inverse statement ...

Migration causes genetic drift.

... but also accepting that other factors are at play. Some better-phrased statements that capture the proposition are as below.

Migration can cause genetic drift. (TRUE)

Migration does not cause genetic drift. (FALSE)

Genetic drift can occur due to migration. (TRUE)

Genetic drift is not a contributing factor to migration. (FALSE)

Genetic drift can occur only due to migration. (FALSE)


From my understanding, you should read the question very carefully and answer the question logically and technically correct. If the examinar had something else in mind that is not written there, and he wanted you to answer the question in a different way, thats not your problem and you can contest the grading.

For your example, from my understanding, the statement can be written in the active form instead of the passive form, without changing the meaning, which makes it more clear what the meaning of the sentence is: "migration causes Genetic drift". Now you can see more easily that the statement is True.

If the statement would be: "Genetic drift is only caused by migration", then the answer would be False.

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