50×0.9228是什么意思

Which of the following will lead Inventories to rise? A inventory—sales ratios are high. B economic activity begins to rebound. C inventory—sales ratios are low. 这题什么原理？

ABC Company sells computer parts by mail. A sample of 25 recent orders showed the mean time taken to ship out these orders was 45 hours with a sample standard deviation of 12 hours. Assuming the population is normally distributed, the 99% confidence interval for the population mean is: A 45 ± 2.80 hours. B 45 ± 6.98 hours. C 45 ± 6.71 hours. 是不是得有表才能做？2.797是怎么来的？

老师好，这道题不是很理解。

老师这两题有什么区别，为什么第一题不选lower？

三题都不会,请老师详解~

老师，是题中本身capital gain distribution, 就是一种有问题的说法吗？那种利得属于capital gain distribution呢？麻烦能举例吗？

请解释一下

Using historical data that was not publicly available at the time period being studied will have a sample with: A Look-ahead bias. B Sample selection bias C Data-mining bias. 这题答案对吗？不应该是前视偏差吧，他确实用的历史数据，只是不公开，能举几个具体例子吗？老师课上讲的范围很大，

A sample of 100 observations drawn from a normally distributed population has a sample mean of 12 and a sample standard deviation of 4. Using the extract from the z-distribution given below, find the 95% confidence interval for the population mean. The 95% confidence interval is closest to: A 7.840 to 27.683 B 11.216 to 12.784 C 11.340 to 12.660 什么时候用12+1.96*4，什么时候用12+1.96*4/100根号下呢？