[SIZE=3]The deterioration of many municipal pipeline networks across the country is a growing concern. One technology proposed for pipeline

rehabilitation uses a flexible liner threaded through existing pipe.

The article "Effect of Welding on a High-Density Polyethylene Liner" (J. of Materials in Civil Engr., 1996: 94-100) reported the following data on tensile strength (psi) of liner specimens when a certain fusion process was used and when this process was not used.

No Fusion :: 2748, 2700, 2655, 2822, 2511, 3149, 3257, 3213, 3220, 2753

Yes Fusion :: 3027, 3356, 3359, 3297, 3125, 2910, 2889, 2902

Compare the mean tensile strengths at the 95% confidence level.

Perform a COMPLETE APPROPRIATE analysis. Answer the question of interest, check assumptions, etc.

My work so far:

For No Fusion: x̅ = 2902.8, n1 = 10, s^2 = 76875.956, s = 277.265

For Yes Fusion: ȳ= 3108.125, n2 = 8, s^2 = 42382.411, s = 205.870

Then,

Sp˛ = 61785.03

Sp = 248.566

S ( x̅ - ȳ ) = 113.953

The part that is confusing me is how to find the degrees of freedom and how to get the t-value.