a fair coin is tossed 4 times with outcomes recorded. define X to be the number of heads recorded. find pr(x=3)

Question

Finite question

Answer 1

Think of the question as follows. You have four blank registers below:

 

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The total number of ways to assign Heads(H) or Tails(T) to each register is 2^4=16, as you should check for yourself.

Now that we know the total number of outcomes, we want to figure the fraction of those that have 3 H. The answer is 4, as there are only four registers where a T can go. Therefore, pr(x=3)=4/16=.25

 

Here is a visualization using the registers:

 

HHHT

HHTH

HTHH

THHH

 

I look forward to answering more of your questions.

-cldp