How Do You Make Something Look Random?

How do you make something look random? Well, let's take your example of the coin. Say i give you a coin and i want you to test to see if it's fair. You'll measure the fraction of times that you get heads or tails. If i somehow arrange to influence you in the tha you do your experiment, i distract you with bananas,. Or I do a silly dance because i know how you flip the corn. Then you're going to measure the coin to be 50 % of time heads - even though it's not. So maybe everything really is determined all the way back to the big bang.