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Statistics in a Modern World 800
Solutions to Exam 2
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- 1st, 4th, average of 7th and 8th, 11th, 14th = 1, 2, 3, 15, 30
- (iii) skewed right/high outliers
- (iii) greater than the median
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- (i) histogram (for values of one measurement variable)
- (iii) scatterplot (for relationship between 2 measurement variables
- (ii) piechart (for one categorical variable)
- (ii) barchart (for two measurement variables)
- (iii) +1 (as students get older, their year at Pitt gets higher, with
few exceptions)
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- z=(95-115)/13=-1.54; the proportion below is .06 or 6%
- highest 1% have 99% below, so z=+2.33, observed value = 115 + (2.33)(13)
= 145.29
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- predicted height = 44.2 + .37(65) = 68.25
- (i) 60 is outside the range of x-values used to produce the regression
line
- r=.5 remains unchanged because it is independent of unit of measurement
- $5(152/167)=$4.55 [Note that the 1995 amount should be less than the 1999
amount of $5.]
- I think (c) is the case, and the graph is cluttered with chart junk.
However, I did not take points off if you believe the graph displayed (a)
or (b).
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- (7)
- 1
- 2
- 4 (the chemical emulsifiers are a confounding variable)
- 5 (but I accepted 6 too)
- 3 (chocolate is a contributing, but not sole, cause)
- 6 (but I accepted 5 too)
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- (i) being male or female may affect your decision to live on or off
campus, but living on or off campus will not affect your gender
- calculate (column total * row total)/table total: 8, 13, 18, 30
- 2, 1.2, .9, .5
- 2 + 1.2 + .9 + .5 = 4.6
- 4.6 > 3.84, so we have statistical evidence of a relationship
- The proportion of males living on campus is 12/26=.46, whereas the
proportion of females living on campus is 9/43=.21. This difference, along
with the answer to (e), lend support to Nancy's claim
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