Applied Statistical Methods 1000
Solutions to Midterm 1
-
- 80, 110, 140, 170, 200, 230, 260
- 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%]
- 170+0.6(30)=188
- (ii) [because it's 1.9 standard deviations away from the mean]
- (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).]
- (c)
- (e)
- (b) [because (a) and (c) would be experiments but (b) would be an
observational study, vulnerable to confounding variables or reverse causation]
-
- (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.]
- (ii) [it would be impractical for such a survey to provide open-ended
responses]
- (d) [because substantially more than half of food shoppers are women,
they should have stratified by gender and sampled a larger proportion of women]
- (d) [all calculations would refer to n=50: the number of trials tells
us the sample size]
- (c) [ask Maddy to explain...]
-
- (i)
- 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)]
- (2-4.27)/13.32=-0.17
- (iii) [the mode, 0, is the smallest of the 3 measures of center reported
in the output]
- (iii) [standard deviation is most impacted by outliers, mean 2nd most]
-
- (vi) [+0.75=positive square root of 0.563]
- (iv) [(596, 597) marked "X"]
- (ii) [(436, 759) marked "R"]
- (i)
- -12.5+1.08(384)=402.2; 392-402.2=-10.2
- (i) [because the size of -10.2 is much smaller than the size of s, 58.79]
-
- (ii) [compare proportion choosing blue for males vs. females]
- 20 percent is the difference between the percentages (ii) in (a)
- 1747/5428=0.32
- (1747/5428)(3574)=1150
-
- (ii) [because restricting ourselves to the condition that B occurs gives
us a smaller denominator, which makes the quotient larger]
- (iii) [because stipulating that B must also occur reduces the probability of A]
- 1-(365/365)(364/365)(363/365)=0.0082
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