设以X，Y分别表示有过滤嘴和无过滤嘴的香烟含煤焦油的量（以mg计），设<img src="https://nimg.ppkao.com/2019-04/wuacheng/2019041615350281282.jpg?sign=655c5a9e317998d670ccc8b95100bfa1&t=62d75dbe" />均未知。下面是两个样本<br /> <img src="https://nimg.ppkao.com/2019-04/wuacheng/2019041615352211275.jpg?sign=3ecf439061cd14045014b8440844c453&t=62d75dbe" /><br /> 两样本独立。求<img src="https://nimg.ppkao.com/2019-04/wuacheng/2019041615354285593.jpg?sign=0a22fa88b23da3582bbcd41a489f7ba8&t=62d75dbe" />的置信水平为0.95的置信区间。