MKSGR:

One title might depend a lot on the car. The next as well. With every title won the chances are getting smaller that it was not based on skill but on luck. If you have 7 like Schumacher you can be pretty sure he was the best. If you have 5 like Fangio same here. And if you have 4 like Vettel - same again Smiley

You still always have to consider the car vs. the competitors' cars. Mathematical probabilities don't apply if the odds aren't really even and one driver is always rolling loaded dice.