Question

2) Now repeat the above test, but treat the whole data file as if it were a random sample of flights. In Statgraphics this is actually much easier than (Q1= Calculate a test for the difference of the average flight departure delay between Southwest Airlines and Alaska Airlines by selecting 10 random flights from each of these two carriers)… In some ways. Select “Compare” from the top menu. Then select Two Samples -> Hypothesis Tests. You will be expected to enter in the sample statistics for each carrier (Southwest and Alaskan Airlines) but be sure to leave the null hypothesis as zero. We have no reason to assume the standard deviation of both groups are the same, so don’t make that assumption in the options

Here is the data from Alaska(AS) and Southwest (WN)

	AS -Alaska	WN -Sowthwest	D (difference)
	-8	-8	0
	-7	1	-8
	0	-6	6
	-7	-6	-1
	-4	-6	2
	9	4	5
	-4	-5	1
	-8	-9	1
	-11	-7	-4
	34	16	18
Avearge	x-bar= -0.6	x-bar=-2.6	d-bar=2
Standard Deviation	13.38	7.99

Answer 1

Null hypothesis:-

Alternate hypothesis:-

Calculation for the test statistic t (because population variance is unknown)

t statistic =

setting the given values from the data table, we get

t statistic =

this gives, t statistic = 0.41

Using the degree of freedom = n-1 =10-1 = 9 and student's t distribution table, we get the following p value

p value = 0.6914

So, p value is insignificant because it is greater than 0.05 significance level.

Thus, we failed to reject the null hypothesis and we can conclude that at 0.05 significance level, there is no significant difference between the means of alaska and southwest