# Thread: Should you guess or leave it blank?

1. ## Should you guess or leave it blank?

On a contest, there are 5 choices, you are given 2 points for leaving a question blank, and 8 points for getting an answer correct. If you had 3 questions you don't know how to do, should you leave them blank or guess? What if you had 1, 2, 4, and 5 questions blank?

How do I calculate the probability of that and the average points you'll get for guessing?

2. Originally Posted by chengbin
On a contest, there are 5 choices, you are given 2 points for leaving a question blank, and 8 points for getting an answer correct. If you had 3 questions you don't know how to do, should you leave them blank or guess?

[snip]

How do I calculate the probability of that and the average points you'll get for guessing?
Let X be the random variable 'number of correct choices'.

X ~ Binomial(n = 3, p = 1/5)

Calculate E(X). So if you guess the answers, E(mark) = 8E(X).

If you leave the questions blank, then you get 6 marks ....

3. Am I doing this right? I completely forgot how to do stats.

8E(X) of B(3,1/5) = 8x3/5 = 24/5?

4. Originally Posted by chengbin
Am I doing this right? I completely forgot how to do stats.

8E(X) of B(3,1/5) = 8x3/5 = 24/5?