Many of these influences overlap, measuring essentially the same force on policy. Some have no effect on policy what- ever. Deleting weak and extraneous variables leaves the best-fitting model. The best fit is the model that gives the simplest, most powerful explanation of tracking policy. I will use the influence of parents in CA 91 to show how the coin-flip sample's change in distribution is computed.
Positive values favor detracking, negative values are opposed.
The negative coefficient means that parent influence decreases the odds of detracking. The coefficient for parent influence means that the odds of detracking decrease by a factor of e - 444, or .641. Raising parent influence by one unit changes the 50-50 sample to 39 detracked schools and 61 tracked, as displayed in Figure 4.4. Parents affect tracking policy. Variables Receiving Special Treatment Community.