You will need either a 7 inch (slightly deep dish) or a 9 inch (shallow) for the pie. If you use a deep dish glass Pyrex that measures 9.5 to 10, you'll probably want to increase the apples to 8 apples and just keep the amount of sugar the same.
Prepare the topping first. Mix the dry ingredients together in a bowl and cut in the butter with a pastry cutter. Keep refrigerated while you make the filling.
Peel, core and cut the apples into very thin slices. Put them in a large bowl and toss with sugar and cinnamon. Lay flat in the dough lined pie dish.
Arrange crumb topping evenly across the apples.
Bake at 450 degrees (425 for glass or Pyrex pan) for 10 minutes, then 350 degrees for 40 minutes.
Let the pie cool completely before you slice it.