NO.PZ2020010303000005
问题如下：
How much probability is within of the mean of a normal random variable?
选项：
解释：
Formally this quantity is 95.45%, but this area is commonly approximated as 95%.
请问为什么可以直接用标准正态分布查表，题目中只说的是normal
NO.PZ2020010303000005 问题如下 How muprobability is within ±2σ\pm2\sigma±2σ of the meof a normranm variable? Formally this quantity is 95.45%, but this area is commonly approximate95%. 这个题目考的是不是置信区间？2倍标准差之间的面积（概率）不应该是68%吗？
NO.PZ2020010303000005 问题如下 How muprobability is within ±2σ\pm2\sigma±2σ of the meof a normranm variable? Formally this quantity is 95.45%, but this area is commonly approximate95%. 已知95%——1.95；99%——2.58，内插法计算？——2，可以吗？
这道题翻译成中文怎么理解呀，应该怎么查表？
老师请问很多查表的题目没给出表，有没有可以下载表的地方。
