Basic Applied Statistics 200
Solutions to Midterm 1

1.  
   1. (v) [comparing proportion in response of interest (survival) for the two explanatory groups (banded vs unbanded)]
   2. (iv) [0.36 is almost twice as high as 0.20]
   3. 28/100=28%
   4. 4 [expected count 0.28(50)=14 is 4 more than the observed 10]
   5. 18+32+10=60
   6. (iii) [C->Q in a two-sample design]
2.  
   1. (i) [Individuals are occupations; for each individual, a pair of values is recorded---typical women's earnings and typical men's earnings.]
   2. (v) [Picture the stemplot rotated with 6's on the left and 9's on the right; there is a somewhat longer right tail, but not extreme.]
   3. 0 [Because there were no values above 100%.]
   4. (iii) [The values range from 61 to 96 so 0.1 and 1.0 would be too small for the typical distance of values from their mean and 100 would be too large.]
3.  
   1. (ii) sigma [It's the mean for the popuation of finches, not a sample.]
   2. 4, 6, 8, 10, 12, 14, 16
   3. 14 [mean plus 2 sds]
   4. 16% [because 68% are between 8 and 12]
   5. mean - 2.5 sds=10-2.5(2)=5
   6. (ii) [because it's 1.75 sds above the mean]
4.  
   1. (v) [positive and moderately strong; positive square root of 0.638]
   2. (ii) [the slope]
   3. (iii) [because the scatter would be reduced and the clustering of points around a line would be tighter]
   4. (ii) [The assignment of roles does not affect the correlation but it does affect the regression line.]
   5. 34.2+0.0473(1934)=126
   6. 156-126=30
   7. (iii) [This is what S tells us.]
5.  
   1. (i) ["By taking advantage of a national registry..."]
   2. (iii) [Before and after makes it paired, comparing women who had abortions with women who gave birth makes it two-sample.]
   3. (i) [Abortion: had one or not; mental health: had contact with mental health professional or not.]
   4. (ii) [Not (i) because "women do not suffer mental health problems...as a result of having an abortion..." but (ii) is correct because "Women who had abortions had higher rates of mental health disorders overall."]
   5. (iv) [Considering these Danish women as a sample, and using their results to draw conclusions about the population of all women in the world.]
6.  
   1. stress
   2. (i) [The researchers lowered stress by reducing unwanted attention, cleaning the cats' litter boxes, and reducing strange noises. These are not factors that can be quantified. In fact, they most likely eliminated as many stressors as possible from cats in the treatment group, so their categorical variable just had two levels: stress reduced or not.]

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