Statistics in a Modern World 800
Solutions to Exam 2
-
- (iii) skewed right/high outliers
- (iv) 23: mean greater than median (outliers pull mean up) but 32 would
be way too high
- (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
- (iii) can't tell for sure, because minimum is anywhere from 14 to 16 and
maximum is anywhere from 34 to 36
-
- (iv) multiple boxplots (for values of one measurement variable compared
for five categorical groups)
- (ii) piechart (for one categorical variable)
- (iii) scatterplot (for two measurement variables)
- (i) -1 because it is a perfect negative relationship
-
- z=(7-12)/2=-2.5; the proportion below is .005, according to Table
- shortest 1% have z=-2.33, observed value = 12-2.33(2)=7.34
- (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]
-
- (i) long term upward trend: fares are increasing
- .60(189.5)/82.4=$1.38
- (ii)$2.50 is too high because $1.38 would have kept pace with inflation
- -92+.0468(2004)=1.79
- +1 because it is strong and positive
-
- (7)
- 5 (slower metaolism is a common cause)
- 1 (TV is a direct cause of obesity
- 3 (TV is a contributing cause to obesity)
- 2 (causation in the opposite direction, with obesity causing children
to watch TV)
- 6 (TV and weight both increasing over time)
- 4 (socio-economic status is a confounding variable)
-
- (i)males: 61/120=.51 as opposed to 89/240=.37 for females
- calculate (column total * row total)/table total: 100, 50, 140, 70
- 1.2, 2.4, .9, 1.7
- 1.2+2.4+.9+1.7=6.2
- (ii) 6.2 > 3.84, so we have convincing statistical evidence of a
relationship
- we cannot claim to know the reason for the relationship as (iii) suggests.
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