Basic Applied Statistics 200
Solutions to Practice Midterm 1

  1.  
    1. (i) 2 categorical variables: use bar graph
    2. (i) compare percentages
  2.  
    1. (iv) 2 quantitative variables: scatterplot
    2. (iv) report correlation
  3.  
    1. mean plus or minus 3 sds: 1.1 to 1.7
    2. z=(1.25-1.4)/=-1.5
  4.  
    1. (ii) firearms (centered around higher numbers)
    2. (iii) both about the same
    3. (iii) both about the same
    4. 21 is middle of upper 5 values
  5.  
    1. 150/360=
    2. 90/240=
    3. (iv) neither: they overlap, and are dependent because P(B) is different from P(B|F)
    4. mutually exclusive (and dependent, because knowing someone ate breakfast tells us the probability of not eating breakfast is zero)
    5. 100, 140, 50, 70
    6. 1+.7+2+1.4=5.1
    7. (i) less than .05 since chi-square is greater than 3.84
    8. (ii) because the percentage eating breakfast is significantly less for females, but we cannot jump to conclusions about the reason for this
  6.  
    1. size
    2. 15.9 (the slope)
    3. (vi) .83 (positive square root of .687)
    4. -141+15.9(40)=495 thousand dollars
    5. 523-495=+28 thousand dollars
    6. 30
  7.  
    1. (ii) and (iii) B and C because no treatment is imposed
    2. (ii) B depends on memory
    3. (iii) C because they are aware of the study as they perform their activities of the day, including watching TV and eating
    4. (i) A because the subjects are not at home
    5. (ii)categorical: whether they are watching TV or not
  8.  
    1. (i) year
    2. (iii) exposure to black and white movies, TV, and photos
    3. don't know/not sure


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