Question

Please interpret the output below. What type of test was used and why? Are energy costs lower for LEED-certified buildings in this output? These data have an effect size of d = .39. How does that add to your interpretation of the results?

	Yearly Energy Costs LEED- Certified Buildings (in thousands of $)		Yearly Energy Costs non-LEED- Certified Buildings (in thousands of $)
Mean	18.22		21.46
Variance	1548.27		1318.33
Observations		60	55
Hypothesized Mean Difference		0
df	73
t Stat	-1.678
P(T<=t) one-tail	0.048
t Critical one-tail	1.667
P(T<=t) two-tail	0.096
t Critical two-tail	1.993

Answer 1

Here student independent sample 't' test was used.

Reason: Here two independent groups are there and also we are testing mean energy costs between two groups.

IT IS A ONE - TAILED TEST

Here research hypothesis is Are energy costs lower for LEED-certified buildings in this output?

Ho: mean difference = 0 Vs. H1: mean1<mean2

Therefore t-statistic = -1.678 and one tailed p = 0.048

Here p <0.05 hence we reject Null hypothesis.

Conclusion: There was an enough evidence that the energy costs lower for LEED-certified buildings

Here effect size of d = .39, it indicates medium effect i.e. likely to be different in the means.