I messed up big-time. The data I have been using over the past few days concerning the DC-CAS included BOTH the regular DC public schools AND the DC charter schools. I thought it was just DCPS. My bad.
I will now attempt to fix that as fast as I can.
One good, unforsee by product is that I think that I will now be able to separate out the overall performance of the entire group of charter schools, without having to do unbelievable amounts of tedious work.
Let me try to explain why by using an example and a small amount of algebra. Suppose two different, large extended families both step on an industrial scale at some warehouse that also acts as an automobile sales emporium. You write down the total weight (W1) of the whole group of people, and count how many people are on the scale (N1). Then one family goes off to go look at a brand-new hybrid flying car, leaving the other family, which happens to have fewer members than the other one. You note the new total weight (W2) of the folks remaining on the scale, and count how many people remain on the scale (N2). It’s easy to calculate the average weight (AW2) of the remaining family (divide W2 by N2), and you can also calculate the average weight (AW1) of the entire group (W1 divided by N1). It turns out that you can also find the average weight of the first family as well – there are a couple of fairly easy methods, depending on exactly what information you are given from the variables I mentioned. I’ll let you think of one.
Oh well, my apologies. Let me get to work at fixing this. If my conclusions change because the data changes, I will let you know.