In each of the following cases, nd the mean, varianceI and standard deviation of the sampling distribution of the sample proportion .3. (a) p = J'. n = 250 (Round variance to 6 decimal places and standard deviation to 4 decimal places. Do not round intermediate values.) (b) p = .2, n = 112 (Round variance to 6 decimal places and standard deviation to 4 decimal places. Do not round intermediate values.) (c) p = .8. n = 395 (Round variance to 6 decimal places and standard deviation to 4 decimal places. Do not round intermediate values.) (d) p = .95. n = 1,035 (Round variance to 6 decimal places and standard deviation to 4 decimal places. Do not round intermediate values.)