how do i find the probability for questions like this? A test consist of 10 true/false questions. to pass the test a student must answer at least 9...

We need to
find the probability that the student guesses correctly on 9 or 10 true false
questions:

(1) The most straightforward way is to use the binomial
distribution. Given the probability p of some event e, the probability of getting x events in n
trials is given as:

`P(e=x)= ` `_nC_x (p^x) (1-p)^(n-x) `

Here x=9 or 10, n=10, and the probability is p=.5 as there is an equally likely chance
of getting the question right or wrong. Since we have 9 or 10, and the events are mutually
exclusive, the total probability is P(x=9)+P(x=10).

`P(x=9)= ` `_(10)C_9 .5^9
.5^1=(10)(1/512)(1/2)=5/512~~.00977 `

`P(x=10)= `...

href="https://en.wikipedia.org/wiki/Binomial_distribution">https://en.wikipedia.org/wiki/Binomial_distribution