这道题说 with a sample standard deviation of 12 hours， 可以算是方差未知吗？

听晕了 X拔到底定义的是什么哦， 抽样样本的平均值吗？比如100个X，n=50,就是说100个数里面抽取了50个数字。 然后这样的抽样过程一致反复，挑选了若干个50个数字的样本。 每个样本去计算一下平均值为X1 X2 X3 。。。。然后这些X1 X2 X3再去算平均值就是X拔吗？

This process is used to estimate the population mean and standard deviation, which usually are unknown. 这题答案里的这句话是不是有错？老师说符合中心极限定理的条件是 known mean and known standard deviation.

P-value中是不是不考虑单双尾检验，只需比较P-value和α的大小即可？

这题解体过程为什么不是12-5=7（nominal rate - inflation = real rate）,7-3=4 (real rate - risk free rate = risk premium)?

F(21) = 1.00 The probability density function for a continuous uniform distribution is calculated as follows: F(X) = (X – a) / (b – a), where a and b are the lower and upper endpoints, respectively. (If the given X is greater than the upper limit, the probability is 1.0.) , 如果below the lower endpoint ，概率是多少?

為什麼組合排列 is least likely to describe the way of calculating the number of labelling

“ask”的例句：A limit buy order is aggressively priced when the limit price is high relative to the market bid and ask prices.这句怎么翻译

老师您好。这里还是不理解。 1.按图中所示，0起点属于第一年的起点，那Year 4不应该是第五年的起点吗，算前几年的股利不应该算到D4吗？ 2.如图所示前四年的估计增长都是15%，D4的股利增长不应该是15%吗？为何用3%？ 3.计算现金流时，为何是最后计算一笔现金流是C03=D3+V3？我理解成应该C03=D3,最后计算的现金流是C04=D4+V4 这个地方没想明白的点比较多，请老师指教！谢谢！

这道题的答案貌似有点对不上啊，求解答