Applied Statistical Methods 1000
Solutions to Midterm 1

1.  
   1. 80, 110, 140, 170, 200, 230, 260
   2. 16, 50 [because 150 is between 140 and 170, the area under the curve to the left is between (100%-68%)/2=16% and 50%]
   3. 170+0.6(30)=188
   4. (ii) [because it's 1.9 standard deviations away from the mean]
2. (a)[The article suggests aspirin DOES help but that it DOES have harmful side-effects. Our potential error in believing these points of view could be (a) but not (b).]
3. (c)
4. (e)
5. (b) [because (a) and (c) would be experiments but (b) would be an observational study, vulnerable to confounding variables or reverse causation]
6.  
   1. (iii) [Even though being conducted online helps to offset dishonest answers, it can't eliminate them; for this question we can't even be sure which direction the bias would go.]
   2. (ii) [it would be impractical for such a survey to provide open-ended responses]
7. (d) [because substantially more than half of food shoppers are women, they should have stratified by gender and sampled a larger proportion of women]
8. (d) [all calculations would refer to n=50: the number of trials tells us the sample size]
9. (c) [ask Maddy to explain...]
10.  
    1. (i)
    2. 3 [1 low outlier, -11, below 0-1.5(3.8-0) and 2 high outliers, 13 and 74, above 3.8+1.5(3.8-0)]
    3. (2-4.27)/13.32=-0.17
    4. (iii) [the mode, 0, is the smallest of the 3 measures of center reported in the output]
    5. (iii) [standard deviation is most impacted by outliers, mean 2nd most]
11.  
    1. (vi) [+0.75=positive square root of 0.563]
    2. (iv) [(596, 597) marked "X"]
    3. (ii) [(436, 759) marked "R"]
    4. (i)
    5. -12.5+1.08(384)=402.2; 392-402.2=-10.2
    6. (i) [because the size of -10.2 is much smaller than the size of s, 58.79]
12.  
    1. (ii) [compare proportion choosing blue for males vs. females]
    2. 20 percent is the difference between the percentages (ii) in (a)
    3. 1747/5428=0.32
    4. (1747/5428)(3574)=1150
13.  
    1. (ii) [because restricting ourselves to the condition that B occurs gives us a smaller denominator, which makes the quotient larger]
    2. (iii) [because stipulating that B must also occur reduces the probability of A]
14. 1-(365/365)(364/365)(363/365)=0.0082

[ Home | Calendar | Assignments | Handouts ]