Statistics in a Modern World 800
Solutions to Exam 2

1.  
   1. (iii) skewed right/high outliers
   2. (iv) 23: mean greater than median (outliers pull mean up) but 32 would be way too high
   3. (iii) 6 is the typical distance of those values from their mean; .06 and .6 would be way too low and 60 would be way too high
   4. (iii) can't tell for sure, because minimum is anywhere from 14 to 16 and maximum is anywhere from 34 to 36
2.  
   1. (iv) multiple boxplots (for values of one measurement variable compared for five categorical groups)
   2. (ii) piechart (for one categorical variable)
   3. (iii) scatterplot (for two measurement variables)
3. (i) -1 because it is a perfect negative relationship
4.  
   1. z=(7-12)/2=-2.5; the proportion below is .005, according to Table
   2. shortest 1% have z=-2.33, observed value = 12-2.33(2)=7.34
5. (d) [(a) not appropriate because heights level off before 20, and the relationship is not at all linear; (b) not appropriate because living situation is categorical]
6.  
   1. (i) long term upward trend: fares are increasing
   2. .60(189.5)/82.4=$1.38
   3. (ii)$2.50 is too high because $1.38 would have kept pace with inflation
   4. -92+.0468(2004)=1.79
   5. +1 because it is strong and positive
7.  
   1. (7)
   2. 5 (slower metaolism is a common cause)
   3. 1 (TV is a direct cause of obesity
   4. 3 (TV is a contributing cause to obesity)
   5. 2 (causation in the opposite direction, with obesity causing children to watch TV)
   6. 6 (TV and weight both increasing over time)
   7. 4 (socio-economic status is a confounding variable)
8.  
   1. (i)males: 61/120=.51 as opposed to 89/240=.37 for females
   2. calculate (column total * row total)/table total: 100, 50, 140, 70
   3. 1.2, 2.4, .9, 1.7
   4. 1.2+2.4+.9+1.7=6.2
   5. (ii) 6.2 > 3.84, so we have convincing statistical evidence of a relationship
   6. we cannot claim to know the reason for the relationship as (iii) suggests.

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