There is no way actual odds were 50-50, they were skewed in British favor from the start.
Say the odds of a British victory in the real-world Battle of Britain stood at 50-50 (there's no real way of knowing what the actual odds are, so we'll just have to select an arbitrary figure). If this were the case, changing the start date of the campaign and focusing only on airfields would have reduced British chances at victory to just 10 percent. Even if a British victory stood at 98 percent, these changes would have cut them down to just 34 percent.
So, they can't calculate the odds from the historical data, but they can calculate the odds for the changes? Yeah, we can file this under ''Pseudoscientific bullshit people make up to pad up the papers''.
The only way the Luftwaffe can start the offensive earlier than in OTL is if they start it before they are fully prepared, which means much worse attrition for the units that open up the offensive.
And constant offensive against the airfields doesn't help either, even during the periods when they were doing it, the attrition rates were unfavorable to Luftwaffe and the British were able to repair the airfields faster than Germans could wreck them. Luftwaffe simply didn't have the numbers to push the RAF into death spiral. Just look at how long it took for Luftwaffe to be be defeated under much worse odds.
Niall MacKay is the Department Head for the University of York's mathematics department, so I don't think this should be dismissed out of hand on the basis of word choice in a news article covering it, rather than assessing the paper based on its own merits. It's linked to in the original post, and the authors did a very good job explaining their methodology. To quote a relevant section, however:
What critical threshold value would constitute the defeat of Fighter Command? As noted earlier, the crux of our method is not to attempt to answer this directly, but rather to calibrate it to prior beliefs using bootstrap methods. Imagine three historians of differing views. One of them believes that the British margin of victory was nil ā that the battle was won on a coin toss ā and thus that the Germans had a probability of victory. A second believes that the British had a modest margin of victory, that it would have taken a moderate amount of deviation from the expected (average) result for the Germans to win, and thus that the British probability of victory was , corresponding to one so-called āstandard deviationā Ļ from the expected (average) value in a normal distribution (a ābell curveā). A third believes that a German victory was very unlikely, and would have taken double such a deviation from the average (a ā2Ļ eventā), and thus (on a bell curve) that the British probability of victory was . We then run a simple bootstrap on the Battle of Britain as actually fought, which results in a bell curve of outcomes centred on the actual outcome, and choose the three values of which generate the three historiansā British victory probabilities specified above.
We then use these three values of in our counterfactual scenarios, resulting for each scenario in three new probabilities. These are robust to small changes in the form of the victory criterion, since this merely mediates between the figures of interest, which are each historianās belief (expressed as a victory probability estimate) about the actual battle, and the belief which it would then be rational for them to assign, on the basis only of the evidence from the actual fighting, to each counterfactual scenario.
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