Asturias56, Easy Street, the issue is not the number of aircraft, but the total threat which has to be managed.
There may only be one TU 95 Bear, but with sixteen long-range, independently targeted, standoff cruise missiles, that aircraft demands a different approach.
So too the context of the conflict; conventional attrition warfare - WW2, a kill rate of 15% could win, in a nuclear conflict then anything less than 100% could be a lost cause; and then all scenarios in between.
Then add the expected (theoretical) effectiveness of the defence, add a bit for practicality, and some more just incase you are wrong, or opposing jamming systems improve, etc.
Also consider the countries involved, technology, political constraint; Vietnam, Middle East, - superiority in any area could be offset by any other; and then who assesses victory - those who define the war crimes.
Are the F15 missiles air to air or air to ground. Could advancing technology enable a dual use missile, air or ground.