Why does a correct guessed answer count as half?

The short answer

Because a correct answer with no reasoning behind it is weaker evidence of understanding than a correct answer with reasoning behind it.

A student who picked the right option and wrote “50/50” has not shown you that they know it. Counting that the same as a student who explained their thinking would give you a deceptive picture of the class’s understanding.

Where the half applies, and where it does not

This is the part worth being clear about, because you will see two different numbers.

The accuracy figure in your results is unchanged. It reports what was actually answered correctly. Nothing is discounted.

The recommendation, the “what to do next” guidance, treats a correct guess as half. It is trying to answer a different question: not “how many got it right” but “does this class understand it”.

So if the recommendation looks more cautious than the accuracy figure suggests it should, that is the discount at work. It is intended.

How an answer gets flagged as a guess

Three ways:

Immediately, where the written reason has no actual words in it, or is obviously random keystrokes. An answer with no written reason at all is never flagged automatically.

Shortly after submission, where the written reason says the student guessed. Phrases like “no idea”, “picked at random”, “50/50”, “coin flip” or “gut feeling”.

When you ask, using Check for guessing on a response’s own menu.

You have the final say

You can mark or unmark any response as a guess yourself, from that response’s menu. Your decision overrides the automatic one.

Pasted answers

Explanations that were pasted in rather than typed are marked separately. The explanations chart on the question results panel breaks written reasons down into groups, so you can see how many were typed, how many look like guesses and how many were pasted.

Pasted is not the same as flagged. It is a signal to look at the response, not a verdict on it.