# Thread: problem on sampling ex 4b q3 ,probability that the total score exceeds 260.

1. ## problem on sampling ex 4b q3 ,probability that the total score exceeds 260.

n unbiased dice is thrown once. Write down the probability distribution of the score X and show that Var(X) = 35/12 = I've done this!!!

The same dice is thrown 70 times.
a) Find the probability that the mean score is less than 3.3.

b) Find the probability that the total score exceeds 260.
is this somewhat related to the first part explain!!!
a part)0.155
b part)0.845

I got the first one but second part T IS THE SUM p(T>260.5) AFTER CC N(245,(14.289)^2), p(Z>1.084)=1-.8586=1.015 BT ANS IS .845 PLS DO SHARE UR IDEAS

2. ## Re: problem on sampling ex 4b q3 ,probability that the total score exceeds 260.

Hey spacemenon.

Hint: What is the distribution of the mean score? (You can either use convolution theorem or a normal approximation to get the distribution of the mean: I would recommend using the Normal approximation).

Once you have the distribution of the mean, you can get probabilities.

The distribution of the mean is related to the Central Limit Theorem.

3. ## Re: problem on sampling ex 4b q3 ,probability that the total score exceeds 260.

plshave a look at the attachments do tell me wat u think

4. ## Re: problem on sampling ex 4b q3 ,probability that the total score exceeds 260.

I'm pretty sure that 0.0417 is the variance of X bar and that 0.2042 is the standard deviation BTW.