问题如下图：
选项：我想问一下有权重的算平均数和方差是不能按计算机的吧
A. 
B. 
C. 
解释：
菲菲_品职助教 · 2018年10月23日
同学你好，是可以的哦，就比如这题：
2ND - 7 - X01=70; Y01=5 - X02=40; Y02=70 - X03=25; Y03=25 - 2ND - 8 - 2ND - ENTER(重复按这一步，直到变成1-V模式 - 往下翻 - 找到σx就是题目要我们求得标准差。
未命名 · 2018年11月11日
太牛了，这个在2，3级别会学到么，这些模式不太懂
菲菲_品职助教 · 2018年11月12日
其实二级就不太会考你标准差的计算这些基础的东西啦，相反二级涉及的计算一般都还是比较简单的，思考的层面和深度会更深一些。跟一级的侧重点不一样哦。
污叫兽 · 2018年12月18日
偷偷问，这个1-v模式是什么模式的缩写？
菲菲_品职助教 · 2018年12月18日
@污叫兽 1-V是一元统计的意思。
Violetta · 2019年06月10日
助教，为什么在这个模式下的x均值和lin模式下的x均值也会不一样呢
FrankSun · 2019年10月28日
老师，算了几遍了，也2nd+ce清零了，按照您的算法，σx是18.708287啊
毛线 · 2019年11月26日
因为出现了lin是线性的意思 这时候要按set调成1-v 就算出来了
NO.PZ2017092702000073 问题如下 The probability stribution for a company’s sales is:The stanrviation of sales is closest to: A.$9.81 million. B.$12.20 million. C.$32.40 million. A is correct. The analyst must first calculate expectesales 0.05 × $70 + 0.70 × $40 + 0.25 × $25 = $3.50 million + $28.00 million + $6.25 million = $37.75 million. After calculating expectesales, we ccalculate the varianof sales: = σ2 (Sales) = P($70)[$70 – E(Sales)]2 + P($40)[$40 – E(Sales)]2 + P($25)[$25 – E(Sales)]2 = 0.05($70 – 37.75)2 + 0.70($40 – 37.75)2 + 0.25($25 – 37.75)2 = $52.00 million + $3.54 million + $40.64 million = $96.18 million. The stanrviation of sales is thus σ = ($96.18)1/2 = $9.81 million. 1
NO.PZ2017092702000073 问题如下 The probability stribution for a company’s sales is:The stanrviation of sales is closest to: A.$9.81 million. B.$12.20 million. C.$32.40 million. A is correct. The analyst must first calculate expectesales 0.05 × $70 + 0.70 × $40 + 0.25 × $25 = $3.50 million + $28.00 million + $6.25 million = $37.75 million. After calculating expectesales, we ccalculate the varianof sales: = σ2 (Sales) = P($70)[$70 – E(Sales)]2 + P($40)[$40 – E(Sales)]2 + P($25)[$25 – E(Sales)]2 = 0.05($70 – 37.75)2 + 0.70($40 – 37.75)2 + 0.25($25 – 37.75)2 = $52.00 million + $3.54 million + $40.64 million = $96.18 million. The stanrviation of sales is thus σ = ($96.18)1/2 = $9.81 million. 请问这道题目可以用金融计算器算吗
NO.PZ2017092702000073问题如下The probability stribution for a company’s sales is:The stanrviation of sales is closest to:A.$9.81 million. B.$12.20 million. C.$32.40 million. A is correct. The analyst must first calculate expectesales 0.05 × $70 + 0.70 × $40 + 0.25 × $25 = $3.50 million + $28.00 million + $6.25 million = $37.75 million. After calculating expectesales, we ccalculate the varianof sales: = σ2 (Sales) = P($70)[$70 – E(Sales)]2 + P($40)[$40 – E(Sales)]2 + P($25)[$25 – E(Sales)]2 = 0.05($70 – 37.75)2 + 0.70($40 – 37.75)2 + 0.25($25 – 37.75)2 = $52.00 million + $3.54 million + $40.64 million = $96.18 million. The stanrviation of sales is thus σ = ($96.18)1/2 = $9.81 million. 1.可不可以再一下为啥求均值就是求期望？2.这里的variance为啥不除以总个数？谢谢
NO.PZ2017092702000073 问题如下 The probability stribution for a company’s sales is:The stanrviation of sales is closest to: A.$9.81 million. B.$12.20 million. C.$32.40 million. A is correct. The analyst must first calculate expectesales 0.05 × $70 + 0.70 × $40 + 0.25 × $25 = $3.50 million + $28.00 million + $6.25 million = $37.75 million. After calculating expectesales, we ccalculate the varianof sales: = σ2 (Sales) = P($70)[$70 – E(Sales)]2 + P($40)[$40 – E(Sales)]2 + P($25)[$25 – E(Sales)]2 = 0.05($70 – 37.75)2 + 0.70($40 – 37.75)2 + 0.25($25 – 37.75)2 = $52.00 million + $3.54 million + $40.64 million = $96.18 million. The stanrviation of sales is thus σ = ($96.18)1/2 = $9.81 million. 答案解析第二步不明白
NO.PZ2017092702000073 问题如下 The probability stribution for a company’s sales is:The stanrviation of sales is closest to: A.$9.81 million. B.$12.20 million. C.$32.40 million. A is correct. The analyst must first calculate expectesales 0.05 × $70 + 0.70 × $40 + 0.25 × $25 = $3.50 million + $28.00 million + $6.25 million = $37.75 million. After calculating expectesales, we ccalculate the varianof sales: = σ2 (Sales) = P($70)[$70 – E(Sales)]2 + P($40)[$40 – E(Sales)]2 + P($25)[$25 – E(Sales)]2 = 0.05($70 – 37.75)2 + 0.70($40 – 37.75)2 + 0.25($25 – 37.75)2 = $52.00 million + $3.54 million + $40.64 million = $96.18 million. The stanrviation of sales is thus σ = ($96.18)1/2 = $9.81 million. 麻烦帮忙一下，谢谢