Statistics in a Modern World 800
Solutions to Exam 4

1.  
   1. (i)
   2. (ii)
2.  
   1. (ii) quantitative (time)
   2. (i) categorical (medication type)
3. (c)neither since the interval contains .5
4. (a)since the intervals do not overlap, and that for 3-yr-olds is entirely above that for 1-yr-olds
5. (b)because smaller samples make wider intervals
6.  
   1. (iv) because the data are paired
   2. (v) because two categorical variables are involved
   3. (i) because one categorical variable is involved
   4. (iii) two-sample z because one measurement (earnings) and one categorical variable (gender) are involved, and the two groups are independent
7. (c) p-value not small means no evidence of a relationship
8. two-sided p-value is double the one-sided p-value
9.  
   1. mean of sample proportions is population proportion .17
   2. standard deviation of sample proportions is square root of (.17)(1-.17)/88 = .04
   3. (iii) this is our guideline for normal approximations
   4. .17 plus or minus 2(.04) = (.09, .25)
10.  
    1. 65
    2. 3/3=1
    3. (i)
11.  
    1. The standard error is square root of .2(1-.2)/400=.02; the interval is .20 plus or minus 2(.02) = (.16, .24)
    2. (iv) because the interval is entirely BELOW .25, instead of being above it
    3. (ii)
12.  
    1. (ii)
    2. (i)
    3. z=(840-1000)/(280/7)=-4
    4. p-value is approximately zero
    5. (i)

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