Basic Applied Statistics 200
Solutions to Midterm 1

1.  
   1. (iv) 2 quantitative variables: use scatterplot
   2. (iv) correlation
2.  
   1. (iii) 1 quantitative and 1 categorical variable: side-by-side boxplots
   2. (iii) compare 5 No. Summaries (because of outliers)
3.  
   1. (i) 2 categorical variables: use bargraph
   2. (i) compare percentages
4.  
   1. (iii) both about the same (both centered in the 70's)
   2. (i) separate lines (distribution more spread)
   3. 56 (3rd of 10 values)
   4. (ii) fairly symmetric
5.  
   1. 0
   2. .0250
   3. .8413-.5=.3413
   4. -1.88
   5. .67 or .68
6.  
   1. mean plus or minus 2 sds: 30 to 90
   2. median=mean=60
   3. z=(50-60)/15=-.67; proportion below is .2514
   4. fastest 20% have .8000 below: z=+.84 and x=60+.84(15)=72.6
7.  
   1. seat position
   2. 423/3253=.13
   3. 190/1000=.19
   4. (ii) passengers in the rear more likely to experience nausea
   5. marginal distribution on the right (923, 1330, 1000)
8.  
   1. moisture content
   2. (ii) soggier because moisture increases as days increase
   3. (vi) .95 (positive square root of .907)
   4. (ii) equation of regression line IS affected by choice of x and y
   5. 2.79+.045(10)=3.24
   6. 3.4-3.24=.16
   7. (iii) extrapolation: 100 is way outside the range 0 to 40
   8. (i) outlier (marked R not X)
   9. (iii) about 30 days, or a month
9.  
   1. (ii) experiment: the treatment is the program
   2. (iii) all students at schools in high crime areas (we may be able to generalize from Seattle to other cities, but we couldn't generalize from high-crime areas to all areas)
   3. 56%-38%=18%
   4. (i) the health teacher could have an impact on pregnancy rates
   5. (iii) random assignment is best
   6. (iii) 2 categorical variables ( program or not, pregnant or not)
   7. (i) compare percentages because there are 2 categorical variables

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