I have this sentence

Persons performing tasks which affect product quality should have appropriate skill and knowledge.

in which I am not sure whether who or which is grammatically correct.

4 Answers 4


It is the task which directly affects product quality, not the person; therefore, the correct word would be which.

By the way, affect should be used in your sample sentence, not effect.

From the Oxford Dictionaries, effect (as a verb) means:

verb [with object]: cause (something) to happen; bring about

The prime minister effected many policy changes.

While affect means:

verb [with object]: have an effect on; make a difference to

The dampness began to affect my health.

  • That I got in word when I used "who" in sentence, while using "which" in sentence is showing grammatical error.
    – Baby Groot
    Dec 8, 2013 at 15:44
  • @Sim Microsoft Word might call it an error, but Word's grammar checker is absolutely horrible. Dec 8, 2013 at 16:00

In the phrase "which affect product quality," the correct word is "which," because the phrase describes tasks, not persons.

  • That's what I thought, but microsoft word is showing mistake in that, it suggests "that" which I don't want to use.
    – Baby Groot
    Dec 8, 2013 at 15:39
  • @Sim PLEASE stop thinking that Microsoft Word has the foggiest idea of how to write. It doesn’t. Turn all that crap off and you will be a lot happier.
    – tchrist
    Dec 8, 2013 at 15:41
  • So Word suggests that, but you are asking if you should use who. That makes no sense at all, sorry. Choosing between tasks that and tasks which is an interesting question, which has been addressed many times before, in fact. But no native speaker would ever find themselves choosing between tasks which and tasks who.
    – RegDwigнt
    Dec 8, 2013 at 17:06

Persons who perform tasks which effect product quality should have appropriate skill and knowledge.

The sentence in question can be rephrased as above. I hope it is easier to understand that 'which' is more appropriate.


I assume that you intend the relative pronoun to refer to tasks. In that case, the relative clause which follows it can be introduced by either which or that, but not by who. Who is used only when the antecedent is a person.

The relative clause is of the defining type, which some think can be introduced only by that and not by which, but they are wrong.

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