Basic Applied Statistics 200
Solutions to Practice Final

 (vi) sidebyside boxplots (comparing values of a quantitative variable
for several groups)
 (iv) scatterplot (looking at the relationship between two quantitative
variables)
 (ii) twoway table (looking at the relationship between two categorical
variables)
 (ii) is matched pairs

 (i) z test about a proportion
 (iv) t test about a mean with onesided alternative
 (vii) twosample t test with twosided alternative
 (ii) z test about a mean with onesided alternative
 (x) inference for regression
 (ix) ANOVA
 (viii) chi square test
 (ii) a 99% confidence interval

 (v) +.6 because it is positive and moderate
 113+36.5(9)=215/5; you should underline s = 75.93
 yes; you should circle the pvalue 0.01
 (ii) prediction interval
 (ii) prediction interval

 (i) observational study; race and layoffs are not treatments that
would be imposed by researchers
 null hypothesis states no relationship between race and layoffs;
alternative states there IS a relationship
 (i) African Americans (.086 vs. .031 for whites)
 AA and Laid Off: 75.3; AA and Not Laid Off: 1434.7
White and Laid Off: 144.7; White and Not Laid Off: 2755.3
 39.7+20.7+2.1+1.1 = 63.6
 (21)*(21) = 1
 Pvalue < .0005
 (i) Pvalue is small, providing evidence of a relationship

 30 plus or minus 2.576 * 3.5/(square root of 25) = (28.2, 31.8)
 (1.96*3.5/2)squared = 11.76; round up to 12

 mean = 15; standard deviation = square root of 60*.25*(1.25) = 3.354
 P(Z>(1815)/3.354) = .1867
 mean = .25; standard deviation = square root of .25*(1.25)/60 = .056
 P(Z>.89) = .1867
 no, because the pvalue is large

 null hypothesis: mu=28; alternative hypothesis: mu>28; t=1.311;
df=63 (use 60); pvalue between .05 and .10, so NO, there is not compelling
evidence that mu>28.
 .10 and .20
 (iii)
 (ii)

 null hypothesis: means equal for SF and LA; alternative: means not equal
 plots of 14 SF values and 16 LA values should be roughly symmetric
(combined sample size is medium, 30)
 df is smaller of 14 and 16, or 13; pvalue between .20 and .30 since
alternative is twosided
 no because the pvalue is large
 circle the StDev's 1.02 and 1.09

 A has highest mean
 B has largest standard deviation

 (ii)
 yes; circle s1, s2, and s3 or s1 (largest) and s2 (smallest)
 null hypothesis: the three means are equal; alternative hypothesis:
not all three population means are equal
 DFG=2, DFE=15; MSG=145.5, MSE=3.7; F=39.3; Pvalue<.001
so we conclude that the mean time is not the same for all 3 groups
 14,3,10,6,11,16
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