If we now look back at the full factorial for 4 factors (see Table 8.12), we will see that Table 8.14 is missing the AD, BD, and CD interactions. If we multiply the -1 and +1 elements in columns C and D, we can see that CD has the same pattern as column AB (see Table 8.15). We could also show that the BD column is aliased with AC and that the AD column is aliased with BC. All of the aliasings generated from the 2^(4-1) fractional factorial in Table 8.14 are presented each at 2 levels to be tested in n = 2^(4-1) = 8nruns, which his half of the full factorial. The notation for a fractional factorial design is 2^(k-p) , where k is the total number of factors in the experiment and q is the number of those factors set equal to an interaction column in a full factorial for k-q factors