Applied Statistical Methods 1000
Solutions to Practice Midterm 1
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- (iv) 2 quantitative variables: use scatterplot
- (iv) correlation
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- (iii) 1 quantitative and 1 categorical variable: side-by-side boxplots
- (iii) compare 5 No. Summaries (because of outliers)
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- (i) 2 categorical variables: use bargraph
- (i) compare percentages
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- mean plus or minus 2 sds: 30 to 90
- z=(78-60)/15=1.2
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- (iii) both about the same (both centered in the 70's)
- (i) separate lines (distribution more spread)
- 5.6 (3rd of 10 values)
- (ii) fairly symmetric
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- seat position
- 250/2000=.125
- 190/1040=.183
- (i) mutually exclusive
- (iv)
- (60+190+850)/2000=.55
- 190/2000=.095
- 120, 130, 840, 910
- (Note that 60 squared is 3600.)
3600/120+3600/130+3600/840+3600/910=66
- (i) much less than .05
- (ii)
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- moisture content
- (ii) soggier because moisture increases as days increase
- (vi) .95 (positive square root of .907)
- (ii) equation of regression line IS affected by choice of x and y
- 2.79+.045(10)=3.24
- 3.4-3.24=.16
- (iii) extrapolation: 100 is way outside the range 0 to 40
- (i) outlier (marked R not X)
- (iii) about 30 days, or a month
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- (ii) experiment: the treatment is the program
- (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)
- 56%-38%=18%
- (i) the health teacher could have an impact on pregnancy rates
- (iii) random assignment is best
- (iii) 2 categorical variables ( program or not, pregnant or not)
- (i) compare percentages because there are 2 categorical variables
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- (ii) Design II
- (i) sample size
- (ii) infants not participating
- (ii) income/education of the mother
- (ii) flip a coin
- (ii) No; mothers could not be blind.
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- (ii),(iii)
- (ii)
- (iii)
- (i)
- (ii)
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