8.1 The subjects are the students in the dorm. The factor is the rate structure. The two different treatments are;
  1. low flat rate
  2. high peak rate, very low off-peak rate.
The response variables are the amount and time of use and the network congestion.
8.3
a) The individuals are the batches, the response variable is the yield.
b) There are two factors and six treatments.
Stirring Rate
60rpm90rpm120rpm
Temperature50C123
60C456
c) 12 individuals are required for the experiment.
8.5 6 rats should be randomly assigned to
Random
Assignment		Group 1
6 Rats		Treatment 1
black tea extract		Compare growth
of cataracts
Group 2
6 Rats		Treatment 2
Green tea extract
Group 3
6 Rats		Treatment 3
Placebo
Using Table B, starting with row 142 and using 2 digits at a time (taking values that are between 01 and 18), with the first 6 going to Group 1, the second 6 going to Group 2, and the remaining going to Group 3. Rats 04, 17, 16, 12, 14, and 09 go to Group 1, 01, 02, 15, 05, 07, and 08 go to Group 2. The rest go to Group 3.
8.7 The design is inferior because it does not take into account conditions that may have changed between years. The most significant is probably the weather. Large differences in the daily temperatures would be likely to make a large difference in the amount of power consumed.
8.9 "Not significantly different that zero" means that the observed very possibly a result of randomness rather than true difference from zero. "Significantly higher" means that the difference observed in that case is unlikely to have been due to chance.
8.11 In this case it would not be possible for the individuals to have no knowledge of which treatment they are receiving, however it would be possible for the treatments to be assigned randomly without the researcher knowing who was placed into each. If this had been done, the experiment would have been blind. Since both the individuals and the researcher knew the treatments, than it is possible evaluations were biased somewhat towards the 'expected' result.
8.19 Methods of making the assignment may vary.
8.21
a)
Women Block
Random
Assignment		Group 1
4 People		Treatment 1Compare differences
Group 2
4 People		Treatment 2
Group 3
4 People		Treatment 3
Group 4
4 People		Treatment 4
Group 5
4 People		Treatment 5
Group 6
4 People		Treatment 6
Men Block
Random
Assignment		Group 1
2 People		Treatment 1Compare differences
Group 2
2 People		Treatment 2
Group 3
2 People		Treatment 3
Group 4
2 People		Treatment 4
Group 5
2 People		Treatment 5
Group 6
2 People		Treatment 6
b) Assignments may vary according to specifics of randomization method.
8.23
a) The subjects were the doctors, the factor was medication and its values were aspirin or placebo. The response variable was heart attack occurance.
b)
Random
Assignment		Group 1
11,000 people		Treatment 1
Aspirin		Compare rates
of heart attack
Group 2
11,000 People		Treatment 2
Placebo
8.31
a) Three of the circles will be randomly selected to receive the CO2.
b) The six circles should be paired off in such a way that the circles with similar levels of fertility are together. Each pair will have one circle randomly chosen to receive the CO2 treatment.
8.33
a) A large group of individuals could be random assigned to have cars with daytime running lights or no daytime running lights. The response variable would be the accident rates.
b) An experiment on running lights is likely to show a larger effect if daytime running lights are relatively uncommon. This effect may not persist if daytime running lights become the norm.
8.37 In order to effectively show a preference between Wendy's or McDonald's burgers in a matched pairs design, each subject should try each burger. The order of tasting should be randomly determined (there may be a general preference for the first burger tasted). There should also be a means of "cleansing the palate" between tastes.
8.40 "Randomized" indicates that the subjects were randomly assigned to the treatment they received. "Double-blind" means that neither the subjects nor the doctors who evaluated them knew which treatment was being received. "Placebo-controlled" means that one of the treatments was a pill that had no active ingredients (called a placebo).
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