Basic Applied Statistics 200
Solutions to Midterm 1 at 10:00

1.  
   1. (iii) 5 number summary values (and boxplots) are higher for males
   2. (iii) Stdev is higher for males, and boxplot shows more spread
   3. (iii) there is some right skewness, and 3 high outliers
   4. (iii) for right skewness/high outliers, mean > median
   5. Five Number Summary is better in the case of skewness and/or outliers
2. 1. stems should be 0 (leaves 12223), 0 (leaves 556), 1 (leaves 00002), 1 (leaves 55), 2 (leaves 00)
   2. no: shape is neither symmetric nor bell-shaped
   3. 10 (the 9th value of 17)
   4. (ii) 6 [the numbers look to be about 6 away from their mean, typically]
3.  
   1. 1-.6700=.3300, or by symmetry look up z=-.44
   2. .0228-.0013=.0215
   3. -1.64 or -1.65
4. 1. 500 plus or minus 2(115): between 270 and 730
   2. x < 300 means z < -1.74; proportion is .0409
   3. the mean, 500
   4. cut-off for top 15% same as for bottom 85%: z= +1.04, so x=500+1.04(115) =619.6
5.  
   1. heights
   2. (i) positive (iii) linear (v) strong
   3. positive square root of .623 (Rsquared) is .79
   4. .79 (r unaffected by change in units of measurement)
   5. -15.4 + 0.364(67) = 9
   6. 8 - 9 = -1
   7. (iii) [the output indicates both R and X for this observation]
   8. (ii) without that student, the points exhibit tighter clustering
   9. (i) a random residual plot indicates a straight line alone is a good summary
6. 1. males: 13/20 = .65 vs 19/54 = .35
   2. 35/42 = .83
   3. 35/74 = .473
7. 1. (i) an observational study; imposing a treatment of meals would be unrealistic
   2. (i)
   3. (iii)
8. 1. Pitt students constitute the population
   2. 3 times 2 = 6
9. 1. (ii) treatment is chewing, so control should be not chewing
   2. (i) randomness avoids bias
   3. (i) adequate replication is another principle of good design

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