Question

New	Current
Sample Size	7	7
Sample Mean	518.2857	561.7143
Sample Standard Deviation	38.9774	27.5058
df
Pooled Sample Standard Deviation	33.7328
Confidence Interval (in terms of New - Current)
Confidence Coefficient	0.95
Lower Limit
Upper Limit
Hypothesis Test (in terms of New - Current)
Hypothesized Value
Test Statistic
p-value (Lower Tail)	0.0165
p-value (Upper Tail)
p-value (Two Tail)

	New	Current
Sample Size	7	7
Sample Mean	518.2857	561.7143
Sample Standard Deviation	38.9774	27.5058
df	10
Confidence Interval (in terms of New - Current)
Confidence Coefficient	0.95
Lower Limit
Upper Limit
Hypothesis Test (in terms of New - Current)
Hypothesized Value
Test Statistic
p-value (Lower Tail)	0.0184
p-value (Upper Tail)
p-value (Two Tail)

IBM is interested in comparing the average systems analyst project completion time using the current technology and using the new computer software package. So, a statistical consultant for IBM randomly selected 7 projects that used the current technology and 7 projects that used the new computer software package. The completion time (in hours) for each project was recorded and then entered into Excel. Assume the samples are independent and from normal populations with equal variances. Can IBM reject the hypothesis μ_New - μ_Current = 0 at α=.01? Based on this paragraph of text, use the correct excel output above to answer the following question.

What is the 95% confidence interval for μ_Current - μ_New?

	a.	(-11.6559, 98.5131)
	b.	(-10.1156, 96.9728)
	c.	(3.2556, 83.6016)
	d.	None of the answers is correct
	e.	(4.1392, 82.7180)

Answer 1

Given that,

For Current : n1 = 7, x1-bar = 561.7143 and s1 = 27.5058

For New : n2 = 7, x2-bar = 518.2857 and s2 = 38.9774

Degrees of freedom = 10

Using t-table we get, t-critical value at significance level of 0.05with 10 degrees of freedom is,

The margin of error (E) is,

The 95% confidence interval for μCurrent - μNew is,

Answer : c) (3.2556, 83.6016)