Found this .

Another justification given for not using objective testing is that candidates can gain inflated scores due to guessing. If you consider the example above then a candidate would have a 1 in 5 chance of correctly guessing the answer. This suggests that it would be easier to pass an objective test.

However, the effects of guessing can be eliminated through a combination of question design and scoring techniques. Those that advocate objective testing suggest a number of strategies. For example, questions could be scored as normal, and a formula for “guess correction” could be applied at the end. There has been a lot of research in this area and a “standard” formula has emerged:

Standard Formula: SCORE = Right - (Wrong/(n-1)).

Right = the number of correct answers.

Wrong = the number of incorrect answers.

N = total number of alternatives per item (including the correct answer)

So, if a candidate answered 35 questions correctly on a 50-question test in which each item had 4 alternatives, the raw score after corrections would be calculated as follows: Score = 35 - (15/(4-1)) therefore Score = 30.

Alternatively, negative scoring could be employed to discourage guessing. The responses to a multiple-choice question might then be scored as follows:

```
+1 for the correct answer
-1 for an incorrect answer
0 for no answer.
```

If corrective scoring is used, it is always important to alert candidates to this, so that they can alter their test-taking strategies accordingly.

https://www.sqaacademy.org.uk/mod/book/tool/print/index.php?id=10654&chapterid=5499

This thread stems from a question I posted on the Mensa subreddit re how guessing might inflate scores on multiple choice questions. One person said to average my scores on an IQ site and reduce by 20% Another said guessing wouldn’t make much difference to the score.

I said I guessed on tests of spatial ability.That I was clueless in working them out. Someone said

Just guessing and getting the correct answer is a “feature” of multiple choice questions. It will apply to everyone who doesn’t know the answer to every question. The person who knows 28/30 and guess on 2 will have a risk of inflating their score just as you who guess on every single question has a risk of inflating your score. If you know that you are guessing on everything then the test is meaningless for you. You are now not measuring your ability but measuring random chance. You ability is actually under what most spatial tests are capable of measuring and all you can get from them is that you are below the normal range.

I said I didn’t guess all answers but knew,or thought I knew,about 3-5 answers out of 30 ie 10-17%. Hence 83-90% were shots in the dark/random guesses.

I do think you can guess better than chance(Jukebox’s example) and worse than chance but it probably evens itself out in the end.

I tried the above mentioned formula on an IQ test I got 12 /30 questions right on with 6 choices per question.

12 - (18/(6-1)) therefore Score = 8.4 . Rounded down=8 . Feel free to correct me if my maths is wrong.

What this tells me given the high/very high amount of guessing because I’m basically clueless is that my spatial intelligence is low/very low. Indeed it is probably lower than the tests indicate because of inflation due to guessing.