An experiment published in The American Biology Teacher studied the efficacy of using 95% ethanol and 20% bleach as disinfectants for removing bacterial and fungal contamination when culturing plant tissues. The experiment was repeated 15 times with each disinfectant, using eggplant as the plant tissue cultured.17 Five cuttings per plant were placed on a petri dish, disinfected using each agent, and stored at 25°C for 4 weeks. The observations reported were the number of uncontaminated eggplant cuttings after the 4 weeks of storage. Relevant data is given in the following table. Are you willing to assume that the underlying population variances are equal?
|
Disinfectant
|
Ethanol
95%
|
20% Bleach
|
|
|
|
Mean
|
3.73
|
4.80
|
|
Variance
|
2.78095
|
0.17143
|
|
a
|
15
|
IS
|
a. What can be said about the attained significance level using the F table in the appendix?
b. Applet Exercise What can be said about the attained significance level using the applet F-Ratio Probabilities and Quantiles?
c. What would you conclude, with α = .02?