Basic Applied Statistics 200
Solutions to Midterm 1

1.  
   1. (vi) sigma (we have information about the popuation, not a sample)
   2. 0, 10, 20, 30, 40, 50, 60
   3. 10 (mean minus 2 sds)
   4. 16% (because 68% are between 20 and 40)
   5. mean - 2.5 sds=30-2.5(10)=5
   6. (iii) (because it's not even 1 sd above the mean)
2.  
   1. (iii) Researchers could have observed who received flowers naturally, or they could have sent the flowers themselves.
   2. (ii) It would be too expensive to send flowers to a large group of subjects. An observational study would be inexpensive, and could include a large number of individuals.
   3. (i) (flowers or no flowers)
   4. (i) Patients who receive flowers from family and friends may receive other beneficial support measures from those people, such as closer supervision of their medical care.
3.  
   1. (iii) The treatment (receiving food or not) was imposed.
   2. (iv) (The experimenters may have sent the dogs other cues besides rewarding their partner or not. Being "upset" is not easy to define. The setting was very artificial.)
   3. (ii) Part (b) illustrates flaws in the study design. "Using several dozen dogs of a variety of backgrounds and breeds" suggests the sampling design is not problematic.
4.  
   1. (i)
   2. (iii)
   3. (iii)
   4. (iv) (Q->Q)
5.  
   1. (iii)
   2. 2 (compare proportions in (a))
   3. 116/874=0.13
   4. (116/874)(437)=58 or 0.13(437)=57
   5. 79 (number in the upper left square)
   6. 79+37+358=474
6.  
   1. (iii) -0.57 (negative and moderate), negative square root of 0.325
   2. (ii) (because the direction is negative)
   3. (iii)
   4. (ii) (discussed in Lecture 12)
   5. 13.8-0.24(31)=6.36
   6. 10.60-6.36=4.24
   7. (iii)(since s=4.36)

Extra Credit: r=0 if s and s_y are close (See Lecture 12).

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