All well and good. The problem is that these errors refer to HYPOTHESES. I think we're still talking about an assertion of FACT ("aliens do exist and are/have visted earth"), so I fail to see what Type I and II have to do with it, as much as you seem to love throwing the terms around.
"A type I error occurs when one rejects the null hypothesis when it is true"
So, in order for me to be committing a Type I error, the existence of aliens would have to be true. Unfortunately, you'll have a hard time convincing me (and many others) that that is true without proof.
"A type II error occurs when one rejects the alternative hypothesis (fails to reject the null hypothesis) when the alternative hypothesis is true."
So what alternative (reality) are you suggesting that I am rejecting, and what PROOF of said reality do you offer?
1. TRADITIONAL TYPE I ERROR: NULL HYP IS TRUE BUT REJECTED
2. TRADITIONAL TYPE II ERROR: NULL HYP IS FALSE BUT ACCEPTED
PUT MORE COMMUNICATIVELY:
3. TYPE I ERROR:
A) The TRUE/objective/tangible/real SITUATION is that NOTHING is there.
B) But the conclusion is that THAT belief is WRONG.
4. TYPE II ERROR:
A) The TRUE/objective/tangible/REAL SITUATION is that THERE REALLY IS SOMETHING THERE.
B) But the conclusion/BELIEF is that NOTHING IS THERE.
With regard to the UFO etc. stuff. . . .
The naysayers typically have the bar--the level of confidence, belief, proof--however one cares to put it--that SOMETHING IS THERE sooooooooooooooo high, that it's virtually a certainty that they will fall victim to a TYPE II ERROR.
Most hereon sound like
They will NOT accept that ANYTHING is there unless and until it lands in THEIR front yard at 12:00 on a Saturday when the Mayor, High School science teachers; nearest college physic profs; CNN, NBC, ABC Presidents and news crews and the New York times science editor all just happen to be over for a BAR-B-Q 30 min before the UFO appears and hangs around for 3 hours sharing BAR-B-Q and giving a presentation on faster than light travel that even Marge Simpson would understand.
WELLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL, EXCUSE ME!
They're going to be waiting a long time for THAT set of contingencies to BE THERE.
UFO's could have landed on the Capital Mall and marched the congress, the bureaucracy, all the lobbyists, the Supreme Court and all the military personnel for a 100 miles around into their huge mother ship and carted them off to Alpha Centauri fully carried live on CNN and THAT contingency would STILL not have happened. And some naysayers hereon sound like they would STILL be crying--DIDN'T HAPPEN! NO PROOF! YADA YADA YADA.
This sort of mentality has always baffled me somewhat, even as a psychologist. Why so much cluelessness? Why does extreme avoidance of a rattlesnake convince them that it's wonderful to play with a Water Moccasin?
BOTH ERRORS ARE DEADLY!
One has to set the criteria realistically. Yet, naysayer after naysayer does NOT DO SO. Why?
Often, it seems truly like pride and an addiction to a mindless sort of religion of scientism. This false conclusion; this false construction on reality that "OBJECTIVE" reality that one can touch and handle and measure with a micrometer is the ONLY REALITY--is absurd.
Smugness based on an extreme TYPE II ERROR is still stupid. One can be just as smugly dead from a TYPE II ERROR as from a TYPE I error.
Court cases demonstrate day in and day out convicting folks to death that expert testimony is a valid route to truth. yet naysayers hereon routinely disavow at a 100% level 100% of ALL expert testimony. That's dumb, stupid, clueless.
Then they sound all super scientifically righteous and erudite in their tones and wording when, in fact, they've just demonstrated abject stupidity--swallowing virtually a certain TYPE II ERROR hook line and sinker without a bobble of awareness that they've done so.
Color me underwhelmed. I'll take my 47 years of honing my screening criteria for puzzle pieces over such blind, mindless addiction to a TYPE II ERROR probability, any day, week, month, year, decade, century, millenium.