(b) Find a 95% confidence interval for a -/, and interpret this interval. Assume population variances are equal. 3. The media selection manager for an advertising agency inserts the same advertisement for a client bank in two magazines, similarly placed in each. One month later, a market research study finds that 226 of 473 readers of the first magazine are aware of the banking services offered in the ad, as are 165 of 439 readers of the second magazine (readers of both magazines were excluded from the survey). (a) Find a 95% confidence interval for the difference in the two proportions. parents. (b) Is there a significant evidence (at the level of 5% ) that two proportions differ