This question was asked to me in one of the interviews.

1. We have a fair coin so when tossed the Probability of getting Heads = 0.5 & Probability of getting tails = 0.5

We plan to toss 200 times in total, after 20 tosses, we have 18 H & 2T

what is the total # of heads we expect by end of the experiment? (N = 200)

Answer:

Since 18H are already given for 20 tosses, we need to find how many heads we will get for the next 180 outcomes

We know that the coin is a fair coin so for the remaining 180 trials the probability of getting heads is 90.

So the # of heads expected by end of trials is 90+18 = 108.