Question

1. A question on a proficiency test is multiple choice with five possible answers, one of which is correct. Assuming that all responses are random guesses, find the probability that among 13 test subjects, at least five answer the question correctly.

(a) .027        (b) .099        (c) .103         (d) .053        (e).901

show how to use on a TI-84

Answer 1

Solution:

We are given that: A question on a proficiency test is multiple choice with five possible answers, one of which is correct.

Thus p = probability of correct answer = 1/5 = 0.2

n = sample size = number test subjects = 13

We have to find: P( At least five answer the question correctly ) =...........?

That is:

We use following steps in TI-84 plus calculator:

Step 1) Press 2ND

Step 2) Press VARS

Step 3) Select binomcdf(

Enter numbers:

Trials = n = 13

p = 0.2

x value = 4

Click on Paste and press Enter.

Thus we get:

Thus

Thus correct option is: b) 0.099