FRAC 6.1: Construct fractional factorial designs
(c) 2009 Design Computing (designcomputing.net/)

Note: Best design for m=4, p=15, and n=28.

try #     	1
seed      	1228966730468
# of iterations	14
f         	7.84 (0)
clear 2fi's	6
det       	4.1747082E12
det*      	0.2479
std. det  	8.1894674E-10
trace V   	2.75

Factor levels:

-1	0	1	0	
-1	1	0	0	
-1	0	-1	0	
-1	-1	0	0	
-1	0	0	-1	
-1	0	0	1	
1	0	0	1	
1	-1	0	0	
1	0	0	-1	
1	0	1	0	
1	1	0	0	
1	0	-1	0	
0	-1	-1	0	
0	0	1	1	
0	1	1	0	
0	1	0	-1	
0	1	-1	0	
0	-1	0	1	
0	1	0	1	
0	0	1	-1	
0	0	-1	-1	
0	-1	0	-1	
0	0	0	0	
0	0	-1	1	
0	-1	1	0	
0	0	0	0	
0	0	0	0	
0	0	0	0	

X'X

28	12	12	12	12	0	0	0	0	0	0	0	0	0	0	
	12	4	4	4	0	0	0	0	0	0	0	0	0	0	
		12	4	4	0	0	0	0	0	0	0	0	0	0	
			12	4	0	0	0	0	0	0	0	0	0	0	
				12	0	0	0	0	0	0	0	0	0	0	
					12	0	0	0	0	0	0	0	0	0	
						12	0	0	0	0	0	0	0	0	
							12	0	0	0	0	0	0	0	
								12	0	0	0	0	0	0	
									4	0	0	0	0	0	
										4	0	0	0	0	
											4	0	0	0	
												4	0	0	
													4	0	
														4	

inverse(X'X)

0.25	-0.125	-0.125	-0.125	-0.125	0	0	0	0	0	0	0	0	0	-0	
	0.1667	0.0417	0.0417	0.0417	0	0	0	0	0	0	0	0	0	-0	
		0.1667	0.0417	0.0417	0	0	0	0	0	0	0	0	0	-0	
			0.1667	0.0417	0	0	0	0	0	0	0	0	0	-0	
				0.1667	0	0	0	0	0	0	0	0	0	-0	
					0.0833	0	0	0	0	0	0	0	0	-0	
						0.0833	0	0	0	0	0	0	0	-0	
							0.0833	0	0	0	0	0	0	-0	
								0.0833	0	0	0	0	0	-0	
									0.25	0	0	0	0	-0	
										0.25	0	0	0	-0	
											0.25	0	0	-0	
												0.25	0	-0	
													0.25	-0	
														0.25	

Note: Clear 2fi's: 12 13 14 23 24 34.
Note: The first 1 columns of the design form the base design.
Note:  FRAC used 0.016 seconds.