A fair coin is tossed 4 times. What is the probability of exactly 2 heads?

\frac{1}{16}

Correct answerYour answer

\frac{1}{4}

Correct answerYour answer

\frac{3}{8}

Correct answerYour answer

\frac{1}{2}

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

$P(X = 2) = {}^{4}C_{2} \left(\frac{1}{2}\right)^{2} \left(\frac{1}{2}\right)^{2} = 6 \times \frac{1}{16}$ .
$= \frac{6}{16} = \frac{3}{8}$ .

Worth noting

$\frac{1}{16}$ is one particular order, such as $HHTT$ ; there are ${}^{4}C_{2} = 6$ orders.

Ten questions from Binomial & Poisson Distributions, at your own pace.

Ten questions from Binomial & Poisson Distributions, at your own pace.

Explanation