Question

The A.P. Statistics exam consists of a multiple-choice section in which each question has five choices. Sara estimates that she has a 75% chance of knowing each question. If she does not know the answer, she will randomly guess.

a) What is the probability of Sara getting a question correct?
b) The A.P. exam has 40 questions, how many might Sara expect to get correct?

Answer 1

@ganeshie8

Answer 2

For the first question A) i got 80% B i got 32

Second i don't quite know how to do it

Answer 3

@ganeshie8

Answer 4

So, let's take a look at each of these.

99.85% of people with HIV test positive. 0.015% of people with HIV test negative.
0.06% of people without HIV test positive. 99.4% of people without HIV test negative.

So, when explaining these values, you simply need to explain what each one means.
Parts b, c and d were given in my explanation :) I hope this helps!