问一道题：NO.PZ2020021205000026

问题如下：

Monthly stock prices are as follows in USD: 35, 38, 41, 37, 33, and 32. Use this data to estimate the volatility per year.

选项：

解释：

The calculations are in the following table. In this case, the average value of the u; is -0.01792 and $\sum_{i=1}^5ui^2$ = 0.03711 and the standard deviation of the u; is $\sqrt{\frac14(0.03711\;-\;5\;X\;0.01792^2)}$ = 0.0942

so that the volatility is 0.0942 $\sqrt{12}$ = 0.326 or 32.6%.

为什么不用E(X）^2(-(E(X))^2呢

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1 个答案

袁园_品职助教 · 2020年03月24日

同学你好！

样本方差是 [ (各个X的平方和) - (均值的平方*n) ] / (n-1) ，标准差是算好方差再开方

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薛真 · 2020年03月30日

谢谢老师

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NO.PZ2020021205000026问题如下Monthly stoprices are follows in US 35, 38, 41, 37, 33, an32. Use this ta to estimate the volatility per year.p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 9.0px Helveticcolor: #454046}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 9.0px Helveticcolor: #464045}span.s1 {color: #6b5147}span.s2 {color: #4b5a6e}span.s3 {color: #303c63}The calculations are in the following table. In this case, the average value of the u; is -0.01792 an∑i=15ui2\sum_{i=1}^5ui^2∑i=15ui2= 0.03711 anthe stanrviation of the u; is 14(0.03711 − 5 X 0.017922)\sqrt{\frac14(0.03711\;-\;5\;X\;0.01792^2)}41(0.03711−5X0.017922)= 0.0942 so ththe volatility is 0.094212\sqrt{12}12 = 0.326 or 32.6%.p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #453f46}span.s1 {color: #777777}span.s2 {color: #466b}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #474047}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #4b434b}span.s1 {color: #303b5f}span.s2 {color: #4b586c}span.s3 {color: #6b5347}span.s4 {color: #303c63}span.s5 {font: 5.0px Helvetica}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #474348}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #4135}p.p3 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #473f46}p.p4 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #453f47}p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #464550}p.p6 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #454048}p.p7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #45434b}p.p8 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #524c4e}p.p9 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #464750}p.p10 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #454047}span.s1 {color: #777777}span.s2 {color: #635e60}span.s3 {color: #4b5a6e}span.s4 {font: 5.0px Helveticcolor: #635e60}span.s5 {font: 5.0px Helvetica}span.s6 {color: #636b73}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #464045}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #453e42}span.s1 {color: #4b5a6e}span.s2 {color: #6b5547}span.s3 {color: #303b5f}span.s4 {color: #5f544f}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #433e44}span.s1 {color: #757575}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #454048}span.s1 {color: #6b5147}span.s2 {color: #303b5f}span.s3 {color: #466b}span.s4 {color: #777373}1、红色表述是不是错了？按照红色线是写成这样的2、1/4和5是什么意思？看了往期解答也不明白3、求年的波动率要用样本方差而不是总体方差？4、0.007097是总体方差，0.084246是样本标准差？不明白，为什么样本直接求出来的居然是总体值？5、若0.007097是总体方差，用它除以（5-1）再开跟号，结果是0.042122，哪里算错了呢？

2024-06-29 21:10 9 · 回答

NO.PZ2020021205000026问题如下Monthly stoprices are follows in US 35, 38, 41, 37, 33, an32. Use this ta to estimate the volatility per year.p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 9.0px Helveticcolor: #454046}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 9.0px Helveticcolor: #464045}span.s1 {color: #6b5147}span.s2 {color: #4b5a6e}span.s3 {color: #303c63}The calculations are in the following table. In this case, the average value of the u; is -0.01792 an∑i=15ui2\sum_{i=1}^5ui^2∑i=15ui2= 0.03711 anthe stanrviation of the u; is 14(0.03711 − 5 X 0.017922)\sqrt{\frac14(0.03711\;-\;5\;X\;0.01792^2)}41(0.03711−5X0.017922)= 0.0942 so ththe volatility is 0.094212\sqrt{12}12 = 0.326 or 32.6%.p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #453f46}span.s1 {color: #777777}span.s2 {color: #466b}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #474047}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #4b434b}span.s1 {color: #303b5f}span.s2 {color: #4b586c}span.s3 {color: #6b5347}span.s4 {color: #303c63}span.s5 {font: 5.0px Helvetica}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #474348}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #4135}p.p3 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #473f46}p.p4 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #453f47}p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #464550}p.p6 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #454048}p.p7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #45434b}p.p8 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #524c4e}p.p9 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #464750}p.p10 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #454047}span.s1 {color: #777777}span.s2 {color: #635e60}span.s3 {color: #4b5a6e}span.s4 {font: 5.0px Helveticcolor: #635e60}span.s5 {font: 5.0px Helvetica}span.s6 {color: #636b73}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #464045}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #453e42}span.s1 {color: #4b5a6e}span.s2 {color: #6b5547}span.s3 {color: #303b5f}span.s4 {color: #5f544f}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #433e44}span.s1 {color: #757575}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #454048}span.s1 {color: #6b5147}span.s2 {color: #303b5f}span.s3 {color: #466b}span.s4 {color: #777373}红色框是怎么计算的呢？ln1.0857是2.6哦？样本方差是怎么酸的？

2024-06-28 16:35 1 · 回答

NO.PZ2020021205000026问题如下Monthly stoprices are follows in US 35, 38, 41, 37, 33, an32. Use this ta to estimate the volatility per year.p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 9.0px Helveticcolor: #454046}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 9.0px Helveticcolor: #464045}span.s1 {color: #6b5147}span.s2 {color: #4b5a6e}span.s3 {color: #303c63}The calculations are in the following table. In this case, the average value of the u; is -0.01792 an∑i=15ui2\sum_{i=1}^5ui^2∑i=15ui2= 0.03711 anthe stanrviation of the u; is 14(0.03711 − 5 X 0.017922)\sqrt{\frac14(0.03711\;-\;5\;X\;0.01792^2)}41(0.03711−5X0.017922)= 0.0942 so ththe volatility is 0.094212\sqrt{12}12 = 0.326 or 32.6%.p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #453f46}span.s1 {color: #777777}span.s2 {color: #466b}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #474047}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #4b434b}span.s1 {color: #303b5f}span.s2 {color: #4b586c}span.s3 {color: #6b5347}span.s4 {color: #303c63}span.s5 {font: 5.0px Helvetica}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #474348}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #4135}p.p3 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #473f46}p.p4 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #453f47}p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #464550}p.p6 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #454048}p.p7 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #45434b}p.p8 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #524c4e}p.p9 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #464750}p.p10 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #454047}span.s1 {color: #777777}span.s2 {color: #635e60}span.s3 {color: #4b5a6e}span.s4 {font: 5.0px Helveticcolor: #635e60}span.s5 {font: 5.0px Helvetica}span.s6 {color: #636b73}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #464045}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #453e42}span.s1 {color: #4b5a6e}span.s2 {color: #6b5547}span.s3 {color: #303b5f}span.s4 {color: #5f544f}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #433e44}span.s1 {color: #757575}p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 8.0px Helveticcolor: #454048}span.s1 {color: #6b5147}span.s2 {color: #303b5f}span.s3 {color: #466b}span.s4 {color: #777373}标准差那个公示没理解，为啥直接是5收益平方和-5均值，感觉少了很多

2024-04-08 01:28 1 · 回答

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2024-03-25 01:42 2 · 回答

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2024-02-29 20:59 3 · 回答

问一道题：NO.PZ2020021205000026

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