Question

4. Experimental design and hypothesis construction; graphing predictions

Imagine that you were studying whether or not a particular genetic mutation increases the risk of developing psoriasis, a skin disorder, in dogs. You have access to 20 dogs that have this mutation, and 20 dogs that do not have this mutation.

1. Write proper, formal null and alternate hypotheses for this experiment.
2. Describe the experimental design you would use to test your hypothesis. You may use the 20 dogs mentioned above; beyond this, you can assume here that you have access to whatever lab equipment you would want to perform this experiment. For each component of the experiment, make sure to say why it is important in a well-designed experiment. You can come up with your own response variable(s) for your experiment; it’s up to your imagination for this question (although make it something relevant to the question!).
3. Draw a graph to show what the data would look like if they supported your alternate hypothesis. In the same graph, show what the data would look like if you could not reject your null hypothesis.
4. Write an explanation of why you drew the data the way you did above for the alternate and null hypotheses (part c).

Answer 1

a) Null hypothesis: There is no association between the particular genetic mutation and risk of psoriasis in dogs.

Alternate hypothesis: There is association between the particular genetic mutation and risk of psoriasis in dogs.

b) The relationship between the genetic mutation and the risk of psoriasis in dogs can be determined by cohort study. The 20 dogs which has genetic mutation will firm the exposed group and the other 20 dogs which do not have genetic mutation form the unexposed group. The development of psoriasis in each of these groups is prospectively studied. The outcome measure is the development of psoriasis. The percentage of dogs developing psoriasis in each group is calculated. They are then analysed using Z test or chi square test to find if there is any significant statistical difference. When the P value us less than 0.05, Null hypothesis is rejected and when it is more than 0.05, Null hypothesis is accepted.

c)

d) I have selected the bar graph to show the difference in the percentage of psoriasis in dogs clearly when the results if the experiment supports Null hypothesis and alternate hypothesis.