Equiprobable events (equally probable events).

You toss an unbiased coin 5 times. Is HHHHH (5 heads in a row) as probable as HTHTH?Answer: Yes.
On the first throw H or T is equally likely. Say it landed H. The coin does not remember what it did on the first throw, so for the next throw H or T is equally likely, so HH is as likely as HT. One can go on in this manner to show that HHHHH is as likely as HTHTH. The probability of HHHHH is 0.5x0.5x0.5x0.5x0.5 This is the same probability as the probability for HTHTH. Equiprobable events are very important in statistics as many problems are solved using equiprobable events.