00:01
For this question, we consider a multiple choice examination that has 50 questions on it.
00:07
And for a student who has done the homework and attended the lectures, the probability of answering any individual question correctly is given as 75%.
00:16
So that's a probability of 0 .75.
00:19
And we are asked what percentage of students who have done their homework and attended the lectures will obtain a grade of 35 or less? so let's first define the random variable x as the number of questions guessed correctly.
00:39
So finding the percent of students who get 35 or less on this exam is the same thing as finding the probability of an individual student getting 35 or less.
00:53
So we want the probability that x is less than or equal to 35.
00:58
Now if we consider our random variable x, each of the questions, each of the 50 questions can be considered at brunuli trial, which is to say that.
01:05
There are two outcomes of interest.
01:08
Either the question is answered correctly or not.
01:12
And it's safe to assume that the outcome for all the, the outcomes for the questions are independent.
01:17
So that is the outcome for one question has no bearing on the outcome for the other question.
01:21
Rather, it's just a probability of 0 .75 for each question...