CK-12 Probability and Statistics - Advanced

6.2. Experimental Design http://www.ck12.org

is the optimum temperature for a higher female ratio and good survival rate, and 280 C is the best

temperature to insure more males (source: Restoring the Tortoise Dynasty, Godfrey Merlin, Charles

Darwin Foundation, 1999.)

2. This would be a blocking design. We would block on species and temperature, so there would be 9
   blocks, 3 of each species, and three at each incubation temperature. There really would not be any
   randomization in this design.


3. (a) There are two treatments, the new medication, and the existing medication. All the subjects could be told
   that they were receiving a new treatment, and then only some would be given the new treatment and the rest
   would be given their original medication. The resulting differences in skin condition between the two groups
   would be compared. (b) You could assign the subjects a different numbering from 1 to 12, but this time
   generating the assignments at random. Then subjects 1-6 would be given the new treatment, and subjects 7-12
   would be given the original medication. Compare the results. (c) In blocking for condition, each block should
   be homogeneous for that trait. So, you would create three blocks: all 4 mild subjects, all 4 moderate subjects,
   and all 4 severe subjects. Then, within each block, randomly assign two subjects to receive the new treatment,
   and two to receive the original. Compare the results.

TABLE6.4:

Pair Number Gender Age

1 F 13

1 F 13

2 F 15

2 F 16

3 F 17

3 F 18

4 M 14

4 M 14

5 M 15

5 M 16

6 M 17

6 M 18

Place the females in chronological order, then group the two youngest, the next two, and the last two. Repeat the
same procedure with the males. This way we have pairs that are similar in both age and gender. One of the subjects
would be chosen at random for the new treatment and the other would receive the traditional medication.

(d) Repeated measures are not a good idea with medication studies as it would be hard to distinguish if the effects
from the repeated treatment are not in fact from still occurring from the presence of the first medication that was
given.