In Class Quiz Questions 2

# In Class Quiz Questions 2 - 4 10T/F Pr[T =0.6 Pr[exactly 8T...

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3.A test consist of 6 multiple choice questions, each with 3 choices, one of which is the correct answer. A student randomly quesses on all 6 questions. Find the probability that the student gets exactly 5 questions correct. 1

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Answered 4/243 CORRECT CORRECT Your answer is only for 4 successes, but the question asks you AT LEAST 4? 6MC, 3 choices Pr[exactly 5 Correct]=? Pr[Correct]=1/3 n=6 Pr[exactly 5 Correct]= k=5 = C(6,5 )∙( ) - = 13 5∙236 5 p=1/3 = 6∙( ) = 13 5∙23 4∙ ( ) = 13 5 1-p=2/3 = 4243
4. A test consists of 10 true/false and the test writer made 60% true. Find the probability that the student guesses on all 10 and gets exactly 8 correct? Answered 0.1209 CORRECT CORRECT Your answer is only for 4 successes, but the question asks you AT LEAST

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Unformatted text preview: 4? 10T/F Pr [T] =0.6 Pr [exactly 8T] =? n=10 Pr [exactly 8T] = C(10,8)∙ ( . ) ( . ) 0 6 8∙ 0 4 2 k=8 =45∙(0.16)∙ ( . ) 0 6 8 p=0.6 = (7.2)∙ ( . ) 0 6 8 1-p=0.4 = 0.120932 5.A skee-ball champion gets a 50-point roll 80% of the time. What is the probability that he will make at least 4 50-point rolls out of 5 attempts? Answer 0.4096 CORRECT CORRECT Your answer is only for 4 successes, but the question asks you AT LEAST 4? Pr[Success]= 0.8 n=5 k= at least 4 → k=4 and k=5 p=0.8 1-p=0.2 Pr[at least 4 Successes]= Pr[4S]+Pr[5S] =C(5,4)∙ . . + , . . = 0 84∙0 21 C5 5∙0 85∙0 20 =5∙(0.2) ∙ . 0 84 + . 0 85 = = . 0 84 + . 0 85 = 0.4096+ 0.32768 = =0.73728...
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