An experiment to determine the efficacy of using 95% ethanol or 20% bleach as a disinfectant in removing bacterial and fungal contamination when culturing plant tissues was repeated 15 times for each disinfectant. The plant tissue being cultured was sweet potato:Five cuttings per plant were placed on a petri dish for each disinfectant and stored at 25 C for 4 weeks.The observation reported was the number of uncontaminated plant cuttings after the 4-week storage.
Disinfectant
|
95% Ethanol
|
20% Bleach
|
|
Sample Size
|
15
|
15
|
|
Sample Mean
|
3.85
|
4.92
|
|
Sample Variance
|
2.75
|
0.18
|
a. Are you willing to assume that the underlying variances are equal? Provide statistical evidence.
b. Using the information from part (a), test statistically if there is a significant difference in the mean numbers of uncontaminated plants for the two disinfectants tested?