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Midterm_2_Sp_11

# A b c panot sp a and not spnot s0308 pbnot sp b and

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A B C P(A|not S)=P( A and not S)/P(not S)=0.308 P(B|not S)=P( B and not S)/P(not S)=0.323 P(C|not S)=P( C and not S)/P(not S)=0.37 P(not S)= P( A and not S)/P(not S)+ P( B and not S)/P(not S)+ P( C and not S)/P(not S)=0.325 So you are most likely to have gone to C. #26-27: Let X be the amount of cash a customer withdraws from their bank account on one visit. Assume X has a normal distribution with mean \$100 and standard deviation \$25. 26. Find the probability that one customer chosen at random withdraws at least \$60. Include a picture in your solution.

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P(X≥60)=P(Z≥-1.6) so prob=1-0.0548=0.9452 ANS_0.9452________ 27. Find the amount of money that represents the cutoff for the top 25% of withdrawal amounts. Include a picture in your solution. Z=0.67 so X=100+0.67*25=116.75\$ ANS__\$116.75_______ #28-30: The number of televisions you sell in a day has this probability distribution: X 0 1 2 3 p(x) .1 .3 .2 .4 28. What is the average number of televisions you sell in a day? ANS____1.9TVs by expectation formula_____ 29. You make \$40 per day plus \$5 for every television you sell. What is your average daily salary? 40+5*1.9=49.5\$ ANS___49.5\$______ 30. The standard deviation of the number of tvs you sell in a day is calculated to be 1.57. What is the standard deviation of your daily salary? Sd(40+5x)=5*sd(x)=7.85\$ ANS__7.85\$________ #31-33: A telemarketer makes phone calls at random trying to sell a product. She knows that 12% of the calls result in the person buying the product. 31. She calls two people at random. What’s the chance of making exactly one sale? 2*0.12*0.88=0.2112 ANS___0.2112________ 32. She makes 10 randomly placed calls. What’s the chance of making no sales? 0.88^10=0.2785 ANS___0.2785________ 33. She makes 10 randomly placed calls. What’s the chance of making at least one sale?
1-0.2785=0.7215 ANS__0.7215_________ #34-35: First year college students were asked what their rank was in high school. The information is summarized below. Rank Top 20% Second 20% Third 20% Fourth 20% Bottom 20% Probabilit y 0.41 0.23 0.29 0.06 0.01 34. Choose two students at random. What is the probability that they are both in the top 20? 0.41*0.41=0.1681 A NS___0.1681____________ 35. Choose two students at random. What is the probability that they are both in the top 40% ? (0.41+0.23)* (0.41+0.23)=0.4096 ANS_0.4096________ 36. FIVE POINTS. Give the first names of BOTH of the TAs in your class. Names only! 4 points for the one TA’s name 5 points for both Tas’ names

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ANSWER SHEET MC AND TF Name_________________________ MIDTERM 2 STAT 133H SP 11 (7 points each) Recitation Time _______________ 1. A B C D 2. A B C D 3. A B C D 4. A B C D 5. A B C D 6. A B C D 7. A B C D 8. A B C D 9. A B C D 10. A B C D 11. A B C D 12. A B C D 13. A B C D 14. A B C D 15. A B C D 16. A B C D 17. A B C D 18. A B C D 19. A B C D 20. A B C D 21. A B C D 22. A B C D 23. A B C D
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A B C PAnot SP A and not SPnot S0308 PBnot SP B and not...

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