Because both links involve the exact same thing, in the exact same context in the exact same sentence. Wikipedia is credible because it actually defines what is what, and short in short everything from offline to online to handheld dictionaries agree on the definition of 'confirmation bias'.
Of course it's freely-editable, so it'll have plenty of trolls the Anita remarks in the entry on Adolf come to mind but it also has a LOT of superusers to fix that because it's popular thanks to being credible and vice-versa. I challenge you to prove otherwise, and if you can't, then... well, you can't argue.
By the way, LolAlytics, LolKing, OP.GG and Champion.GG DO display the same info: champion pick-rates, builds, and all but one have the ability to skew it based on division and rank. You're using ONE site, and then getting asshurt when someone tells you to use more than what just confirms what you think.
It helps you later in life, too, so...
Being able to check multiple sources for info, that is. It prevents bias, and in turn confirmation bias... which is looking for evidence that supports what you claim and... denying all other evidence contrary. ;)
Oh by the way, LolKing, LolAlytics. OP.GG all say that he evens out at 48% after 15~ games played on average. So... three sources beat one.
I didn't fact-check this. I want you to try and genuinely prove me wrong.
Edit: Removed a link. I don't want to be a hypocrite.
Edit2: Rakan's LoLGraphs profile doesn't seem to exist.