Statistics in a Modern World 800
Solutions to Practice Exam 3

1. 1-.3=.7
2.  
   1. yes; you can be male or female but not both
   2. yes; .6*.5=.3
   3. .6+.5-.3=.8
   4. 1-.8=.2
3.  
   1. (a) 1/2
   2. (ii) gambler's fallacy
4.  
   1. (a) 1/4 * 1/4 = 1/16
   2. (ii) independent
5.  
   1. 5/6 * 5/6 = 25/36=.69
   2. 1 - 25/36 = 11/36 = .31
   3. (i) relative frequency
6. 1(.1)+2(.5)+3(.3)+4(.1)=2.4
7. (c)
8. (v) optimism
9. (a) anchoring
10. (b) second is different from the first and third is different from both of them
11. (c) this is the opposite of #10
12. (g) conservatism
13. (g) pseudo-certainty effect
14. (a) (more general)
15. (d) representativeness
16. (c)
17. (b)
18.  
    1. first branch-off: spy or not spy, with probabilities .001 and .999; second branch-off: incriminated or not, with probabilities .8 and .2 for the spies, .16 and .84 for the non-spies
    2. .001(.8)=.0008
    3. .999(.16)=.15984
    4. .0008+.15984=.16064
    5. .0008/.16064=.00498
    6. (d) confusion of the inverse

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