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TEST THREE PROBABILITY AND STATISTICS, ECON 15A
NOVEMBER 4, 2011 l. The probability that a student is absent ﬁ‘onr class is 40%. The probability that a student is sick is 20%. The chance that a student is
both sick and absent is 10%. Find the probability that the student is sick, given that he is absent. A‘ Aeaazm' BA we): .10 5
6: 510.4 PC I > 196A) 7123 2. At the UCI cafeteria, 80% of the people buy a bag of chips. Of thdse people, 50% also purchase a brownie. What is the chance that
a person buys chips and a brownie? t‘hﬂx .50 r: 3. Not counting trivial cases, if two events are mutual] exclusive, they are: A) always independent, B) sometimes independent, C) never independent. No need to explain. 4. There is a vase with three green balls, four ye ow a s, and ﬁve orange balls. If you calculate the probability of drawing an orange
ball as 5/ 12, which method of assigning probabilities are you using? A6? A $721012»! 1:39;] 045.55%; i622 MW 5. Using the same vase as in question 4: What is the probability of picking two balls (without replacement} and getting two green
balls? 
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5 Z 4 A: x A. 6. Using the same vase as in question 4: What is the probability of picking two balls (without rcpiacement) and getting either a yellow
ball on the ﬁrst pick or an orange ball on the second pick? 4 '5“ we» was» 03> (we
B290 F6 Marti/z :E/ZXSII Using the same vase as in question 4: What IS the probability of picking three balls and g at least one yel FCAUBUCD I—* $903303 06)
i“(<%2 x741 x é/[o 8. Using the same vase as in question 4. Amy has to reach into the vase and aw bails until she gets a green ball. When she draws her
first green ball, she stops and draws no more balls. What' 1s the probability that she drew the green ball on her fourth try? A' agrqizam C: 399 wréiﬁwu PCA>X PCDDXPZG> yPCp)
e WIOJTCZBEBJ D Whézeeu (3/12. x ”0/” x 1/”) x 3/5; 9. 45% of planted ﬂowers receive fertilizer If the ﬂowers receive fertilizer, they grow to their ﬁll] height. If they do not receive
fertilizer there IS only a 20% chance of growing to their ﬁll] height. You see a planted ﬂower hat has grown to it full height. What Is the probabihty that It received fertilizer A, )1 CELL.
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