If the mean of the following probability distribution is 3.44, what is the variance? 3 4 P(X=x) 0.23 0.37 0.13 0.27

3

Suppose that we have disjoint normal populations A and B with equal population variances. Suppose we plan a sample of size 4 from from population A and a sample of size 9 from population B which we will pool to form the pooled variance. If you know the population variances are both in fact equal to 6, what is the probability that the pooled variance of the two samples will turn out to be less than 8 given your information? .8 .2 .82 .18 NONE OF THE OTHERS

Suppose that for a given computer salesperson, the probability distribution of x = the number of systems sold in one week is given by the following table. x 1 p(x) 2 3 4 5 0.06 0.10 (a) Find the mean value of x (the mean number of systems sold). 0.11 0.30 6 7 8 0.29 0.12 0.01 0.01 (b) Find the variance and standard deviation of x. (Round your standard deviation to four decimal places.) variance standard deviation How would you interpret these values? (Round your standard deviation to four decimal places.) The mean squared deviation from the mean number of systems sold in one week is A typical deviation from the mean number of systems sold in one week is (c) What is the probability that the number of systems sold is within 1 standard deviation of its mean value? (d) What is the probability that the number of systems sold is more than 2 standard deviations from the mean?