An experiment was conducted to evaluate the effect of seedin

An experiment was conducted to evaluate the effect of seeding clouds on rainfall with silver nitrate. 26 of 52 clouds were randomly selected to receive the seeding, the other 26 had no seeding (a control). The resulting data are provided below. Assume equal variances and conduct a statistical comparison of the mean rainfall. What conclusions do you draw? Conduct a test for equality of variances between the seeded and unseeded data. What conclusions do you draw? Assume unequal variances and conduct a statistical comparison of the mean rainfall. What conclusions to you draw?

Solution

a) Assuming equal variance:

H0: Means of two groups are same

H1: Atleast one group is same.

Alpha: 5% Level

Test statistic:

From Excel

Conclusion: t cal=3.3254

t critical value=2.063

t cal > t critical value we reject the Ho

C)

H0: Means of two groups are same

H1: Atleast one group is same.

Alpha: 5% Level

Test statistic:

From Excel

When unequal variances

t-Test: Two-Sample Assuming Unequal Variances

Conclusion: t cal=3.3254

t critical value=2.16037

t cal > t critical value we reject the Ho

t-Test: Two-Sample Assuming Equal Variances
	seeded	unseeded
Mean	85.30769231	21.15384615
Variance	4683.730769	154.6410256
Observations	13	13
Pooled Variance	2419.185897
Hypothesized Mean Difference	0
df	24
t Stat	3.325406609
P(T<=t) one-tail	0.001415331
t Critical one-tail	1.71088208
P(T<=t) two-tail	0.002830662
t Critical two-tail	2.063898562