Skip to main contentSkip to solution

Which of the following are true ?

(A) If the mean of a normal variate is 12 and standard deviation is 4, then the Z-score of data point 20 is 2.

(B) Mean of the numbers obtained on throwing a die having '1' on three faces, '2' on two faces and '5' on one face is 3.

(C) If the variance of a Poisson's distribution is 2, then P(X=0)=1e2P(X=0)=\frac{1}{e^2}.

(D) For a binomial distribution, mean = 9 and the standard deviation is 32\frac{3}{2}, then the number of trials is 12.

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 4

(A): z=20−124=2z=\frac{20-12}{4}=2, true. (C): variance 22 gives λ=2\lambda=2, so P(X=0)=e−2P(X=0)=e^{-2}, true. (D): np=9np=9 and npq=94npq=\frac{9}{4} give q=14q=\frac{1}{4}, p=34p=\frac{3}{4} and n=12n=12, true.

(B) is false, since the mean is 3(1)+2(2)+1(5)6=2\frac{3(1)+2(2)+1(5)}{6}=2, not 33.

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question