Question

A coin is tossed 7 times. What is the probability that the number of heads obtained will be between 2 and 7 inclusive? Express your answer as a fraction or a decimal number rounded to four decimal places.

Answer 1

0.9375

Explanation:

Given the following :

Number of coin tosses = 7

Probability that number of heads obtained will be between 2 and 7 inclusive?

x = 2,3,4,5,6,7

Probability (P) = number of required outcomes / total possible outcomes

For a coin toss = 1 Head (H), 1 tail (T)

P(H) = 1 / 2

P(X) = C(7,x) * (1/2)^7

P(X) = C(7, x) / 0.5^-7

P(X) = [C(7,2) + C(7, 3)+ C(7,4) +C(7,5) + C(7,6) +C(7,7)] / 128

P(X) = (21 + 35 + 35 + 21 + 7 + 1) / 128

P(X) = 120 / 128

P(X) = 0.9375