Question

when taking a 19 questions multiple choice test ,where each question has 3 possible answer, mor questions correct by guessing alone.how can I find if is an unusual to be more than two standard deviation away from expected

Answer 1

We will have the following:

*There is a 1/3 chance for each question.

`p=(19)((1)/(3))\Rightarrow P=(19)/(3)\Rightarrow P\approx6.3`

So, you should get about 6 answers correctly by guessing alone.

***We have that an unusual event is if the probability of it occurring is less than 5%. 2 in standard deviation is well greater than this, so it should not necessarily be considered unusual.