Question

how to make sample space if a coin is tossed four times?

Answer 1

coin tossed once, sample space has 2^1 = 2 elements H,T
coin tossed twice, sample space has 2^2 = 4 elements HH,HT,TH,TT
try for 3 and 4

Answer 2

for 4, the sample space will have 2^4 = 16 elements.