Scale deposits can cause a serious reduction in the flow performance of a well. A study published in the Journal of Petroleum and Gas Engineering (Apr. 2013) compared two methods of estimating the damage from scale deposits (called skin factor). One method of estimating the well skin factor uses a series of Excel spreadsheets, while the second method employs EPS computer software. Skin factor data was obtained from applying both methods to 10 randomly selected oil wells: 5 vertical wells and 5 horizontal wells. The results are supplied in the accompanying table.
a. Compare the mean skin factor values for the two estimation methods using all 10 sampled wells. Test at a = .05. What do you conclude?
b. Repeat part a, but analyze the data for the 5 horizontal wells only.
c. Repeat part a, but analyze the data for the 5 vertical wells only.
Skin Factor Values

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Well (Type) Excel Spreadsheet EPS Software 1 (Horizontal) 2 (Horizontal) 3 (Horizontal) 4 (Horizontal) 5 (Horizontal) 6 (Vertical) 7 (Vertical) 8 (Vertical) 9 (Vertical) 10 (Vertical) 44.48 18.34 37.77 13.31 7.02 19.21 11.70 9.25 4.77 1.96 317.40 281.74 181.44 192.16 140.84 154.65 77.43 56.86 49.37 45.01