SOLUTION: Mrs. Hudson plans to give a 10 question multiple choice exam in which each question has 4 options. Each question counts for 1 point. A score of 8 or more is a passing score while

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Question 1033163: Mrs. Hudson plans to give a 10 question multiple choice exam in which each question has 4 options. Each question counts for 1 point. A score of 8 or more is a passing score while 7 or less is a failing score. The probabilities of guessing a certain number of questions correctly are listed in the table below.
Number of Questions Correct
Probability for Guessing Correctly
0
0.05631351
1
0.18771172
2
0.28156757
3
0.25028229
4
0.14599800
5
0.05839920
6
0.01622200
7
0.00308990
8
0.00038624
9
0.00002861
10
0.00000095

I. Compute the probability of answering 8 or more questions correctly by calculating the probability with a direct sum and by using complements.
How do the two approaches compare?

Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Direct sum
P%28X%3E=8%29=P%288%29%2BP%289%29%2BP%2810%29
Complement

Direct sum has fewer terms.