HW3_Sol

HW3_Sol - cor(data,2,data,3*2 d It changes its sign to...

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Homework 3 Solutions 1) Read Chapter 6 (only sections 6.1 and 6.7). 2) a) The median is \$118,000 found by: data<-read.csv("OH_house_prices.csv",header=F) median(data[,1]) This is much smaller than the mean of \$190,317.60 found by mean(data[,1]) b) This suggests the data is right skewed. c) The median increases by 10 (thousand dollars) to \$128,000. median(data[,1]+10) d) The median doubles. median(2*data[,1]) e) data[1:10,1]<-data[1:10,1]+29000 The median is not changed but the mean increases to 219.3176 = \$219,317.60 which is an increase of 29 = \$29,000.

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3) a) 8.315218 found by ages<-c(19,23,30,30,45,25,24,20). sd(ages) b) a. = X 216/8=27 7 ) 27 20 ( ) 27 24 ( ) 27 25 ( ) 27 45 ( ) 27 30 ( ) 27 30 ( ) 27 23 ( ) 27 19 ( 2 2 2 2 2 2 2 2 - + - + - + - + - + - + - + - = s 315 . 8 7 484 = = s c) It does not change. sd(ages+10) d) It is multiplied by 100. sd(100*ages) 4) a) The correlation is 0.6537691 found by: data<-read.csv("football.csv") cor(data[,2],data[,3]) b) It does not change. cor(data[,2],data[,3]+10) c) It does not change.

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Unformatted text preview: cor(data[,2],data[,3]*2) d) It changes its sign to become negative. cor(data[,2],data[,3]*-2) 5) Do Chapter 6 textbook problem #2 (parts a,b,c,d only) on page 404. a) b) No, confidence is not a symmetric measure. c) d) 6) Do Chapter 6 textbook problem #3 (parts b,c,d only) on page 405. b) c) d) Yes, it is possible. Many such examples can be constructed. 7) Do Chapter 6 textbook problem #6 (parts d,e only) on page 406. d) s({Bread, Butter}) = 5/10 is the largest support using for an itemset of size 2 or larger. e) from the ICE we saw c({Bread} → {Butter}) =1 = c({Butter} → {Bread}) also, the following all work c({Milk} → {Bread}) =.6 = c({Bread} → {Milk}) c({Milk} → {Butter}) =.6 = c({Butter} → {Milk}) c({Beer} → {Cookies}) =.5 = c({Cookies} → {Beer}) c({Beer} → {Bread}) =0 = c({Bread} → {Beer}) c({Beer} → {Butter}) =0 = c({Butter} → {Beer}...
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This note was uploaded on 08/20/2011 for the course STATS 202 taught by Professor Taylor during the Summer '09 term at Stanford.

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HW3_Sol - cor(data,2,data,3*2 d It changes its sign to...

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