Please help with the statistics problem, thanks!?

Question

An experiment to determine the efficiency of using 95% ethanol or 20% bleach as a disinfectant in removing bacterial and fungal contamination when culturing plant tissues was repeated 15 times with 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 eggplant cuttings after 4-week storage.
Disinfectant 95% Enthanol 20% Bleach
Mean 3.73 4.80
Variance 2.78095 0.17143
n (sample size) 15 15
Pooled variance = 1.47619
(a) Are you willing to assume that the underlying variances are equal?
(b) Using the information form part a, are you willing to conclude that there is a significant difference in the mean numbers of contaminated eggplants for the two disinfectants test?

Answer 1

to test for equal variance, use the two-sided F-test with 14,14 dof.

H-naught, the two variances are equal, H-alternate, there are unequal.

Let α=5%

FF(α/2)
F=2.78095/0.17143=16.222

F(critical)=2.48

Therefore reject H-naught. The variances are not equal.

For the second use t-test with 28 dof

use same α=.05, but 2-sided so t-crit=2.048
because the variances are unequal use

t=(x1-x2)/sqrt(s1^2/n1+s2^2/n2)=2.41>2.048 so reject H-naught