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Unformatted text preview: The roulette wheel has 38 slots numbered 1
36, 0 and 00. a) What is the appropriate box model? Draw the box. 3 tickets marked “11” and 35 tickets marked “
1” b) How many draws from the box? ___100________ (1 pt.) c) What is the average of the box? Write your answer as a fraction. (2 pts.) (3(11) + 35(
1))/38 = (33
35)/38 =
2/38 d) What is the SD of the box? Show work. Circle answer. Round your answer to 2 decimal places. (2 pts.) −
SD = 11− 1 3 35
≅ 12 x 0.27 = 3.24 ×
38 38 e) Use the normal approximation and the fact that the EV is about $
5 and the SE is about $32 to figure the chance that the gambler will win more than $3 in 100 plays? €
€i)
€First calculate the Z score. Show work. Circle answer. (2 pts) Z = value
EV/SE Z= (3
5)/32 = 0.25 ii)
Now accurately mark z on the normal curve below and shade the correct area . Circle your answer. (2pts) Sorry, I couldn’t draw the picture here, but here’s how to do the problem: Look up Z=0.25 on Normal Table to get middle area = 20%, the area above Z=0.25 is then (100
20)/2 = 40% 3) 100 draws are made at random with replacement from the box containing 7 tickets: 0 2 3 4 6 The SD of the box is 2. a) The Expected Value fo the average of the 100 draws is ____3 (same as ave of box). b) The Standard Error of the average of the 100 draws is ___0.2__________. SEave = 2/sqrt100 = 0.2 c) Use the normal approximation and your answers from (a) and (b) above to find the chance that the average of the draws will be more than 3.4. i)
First calculate the Z score. Show work. Circle answer. (2 pts) Z= (3.4 – 3) /0.2 =2 ii) Now accurately mark z on the normal curve below and shade the correct area . Circle your answer. (2pts) Sorry, I couldn’t draw the picture here, but here’s how to do the problem: Look up Z=2 on Normal Table to get middle area = 95%, the area above Z=2 is then (100
95)/2 = 2.5% Page 8 Study Guide KEY for Exam 3 Chapter 16 – Sample Surveys • • • Random Surveys (subjects are randomly selected) are best for 2 reasons: 1. Eliminate selection bias 2. May be translated into box models so SE’s can be calculated. Self
selected surveys (surveys posted on internet where anyone can respond) have the worst selection bias. Non
response bias and bias in the wording of question is a possible problem for all types of surveys. 1) Does a simple random sample eliminate the following sou...
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 Spring '08
 Kim
 Statistics

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