Problem N5627 probability theory confidence interval

5627. In the order of random re-sampling, a survey of 400 workers of a certain enterprise was carried out, as a result of which it was found that the average wage of workers is 7,000 rubles. Determine with reliability 0.9544 the possible limits of workers' wages, assuming the distribution of workers' wages to be normal with a mean square deviation of 180 rubles.