The Application of Response Surface Methodology in the Investigation of the Tribological Behavior of Palm Cooking Oil Blended in Engine Oil

Table 7

Analysis of variance for coefficient of friction (COF).

Source	DF	Seq SS	Adj SS	Adj MS	value	value
Regression	9	0.069229	0.069229	0.007692	462.37	0.000
Linear	3	0.058443	0.002365	0.000788	47.39	0.005
Square	3	0.010525	0.007339	0.002446	147.04	0.001
Interaction	3	0.000261	0.000261	0.000087	5.23	0.104
Residual error	5	0.000050	0.000050	0.000017
Lack of fit	3	0.000050	0.000050	0.000050	3741.13	0.000
Pure error	2	0.000000	0.000000	0.000000
Total	14	0.069279

= 0.00407874, PRESS = , = 99.93%, (pred) = %, and (adj) = 99.71%
DF: degrees of freedom; Seq SS: sequential sum of squares; Adj SS: adjusted sum of squares; Adj MS: adjusted mean squares.