All along in this course I have been

teaching you terminology and techniques, but what I have really been doing is

giving you tools. Now we start the part of the course in which you will learn to

use these tools in specific ways. No longer is the task to use the hammer of

sum of x divided by n to pound a central tendency nail. Now you will use all of

your statistical tools, follow hypothesis testing instructions, and build a real

statistical analysis. I’m going to teach you about hypothesis testing. So that

means that we develop a hypothesis and we test it, right? What makes this part of

statistics difficult is when we decide what hypothesis to test. Many students

are surprised to learn that we do not begin with a hypothesis that we would like, to prove but rather, we begin with a hypothesis that nothing happened. We’re

going to posit two explanations, two hypotheses for our research, the first

the hypothesis we actually test, is the null hypothesis, which says that no

differences exist; there was no effect. The best explanation is chance, and here

is why we begin with the null hypothesis and we don’t begin with the hypothesis

that we would like to prove. It’s ancient aliens guy from The History Channel!

Ancient aliens guy is an internet meme about a guy on a television show about

aliens. No matter what the topic is, his explanation is always aliens. He can find

evidence for aliens wherever he looks. Fundamentally the problem with his

approach is that he begins with the alternative hypothesis, not the null

hypothesis. He begins with his explanation that everything unknown,

unknowable, or misunderstood can be explained by aliens. If scientists,

historians, researchers are still searching for answers, he steps into that

gap with his explanation. Aliens did it!

Starting with an alternative hypothesis leads us astray in so many ways,

conflating possibility with probability. I mean can you prove that aliens didn’t

build the Egyptian pyramids and Stonehenge? If you can’t prove it didn’t

happen then how can you say aliens didn’t do it, I mean anything is possible!

The answer is we’re not trying to prove anything. We’re looking for the most

likely explanation with the fewest assumptions, the most parsimonious

explanation. I can’t prove that you were not miraculously transported home last

night by supernatural means, but most likely you drove home. Overvaluing

certainty, ancient aliens guy would really really believe that aliens make

crop circles and abduct Texans. He might say that “You scientists are always

talking about probability and likelihood, but you can never be certain about

anything like I am!” Well my answer to that is that certainty is overrated, and

usually a refuge for people who don’t actually have evidence. Lots of people

claim to be certain that they know what happens to us Homo sapiens after we die,

but as a critical thinker you should never accept the certainty of someone

who could not possibly know what they claim to be so certain about. All

ignorance is equal. The argument from ignorance leaves no way to judge whether

other hypotheses are correct or not. If all that is required is a gap in

knowledge, an opening of ignorance, a question that science is still figuring

out, then any crackpot supernatural extraterrestrial explanation is just as

good as any other. Once you abandon evidence as your standard for belief,

there’s no way to choose between competing theories and non-falsifiability. When scientists show how Easter Island was really constructed,

that doesn’t undermine ancient alien guy’s alien hypothesis, just because he

was wrong about Easter Island doesn’t mean the aliens didn’t kill the

dinosaurs, or castrate the heaven’s gate cult guys, or leave behind their crystal

skulls. His alien hypothesis can never be proven false no matter how many times he is proven wrong. True believers and conspiracy theorists start with the

conclusion, and then look for evidence to support it. They ignore the evidence that

does not support their predetermined conclusion, but not only is that not

honest, it’s not necessary. Only if you want to believe in aliens are aliens a

plausible explanation. Aliens are not required. It works without that

assumption and we can do better. So let’s do some science.