一組共10個的數據由小至大排列如下:
-1.4 , -1.2 , 0.3 , 2.5 , 2.5 , 3.2 , 5.6 , 6.8 , 7.1 , c
已知方差為 10.31
求c
F.7 數學方差問題1
2009-10-28 5:04 am
回答 (2)
2009-10-28 6:27 am
✔ 最佳答案
平均值 m = 總數 / 10m = (-1.4 -1.2 + ... + 7.1 + c) /10
m = (25.4 + c)/10
方差 = [(-1.4)^2 + (-1.2)^2 + ... +(7.1)^2 + c^2]/10 - m^2
= (154.24 + c^2) / 10 - [(25.4 + c)/10]^2 = 10.31
1542.4 + 10c^2 - 645.16 - 50.8c - c^2 = 1031
9c^2 - 50.8c - 133.76 = 0
c = {50.8 +/- √[50.8^2 + (4)(9)(133.76)]}/18
c = 7.6或1.9556(不合)
2009-10-28 5:06 am
8.91!!!!!!
收錄日期: 2021-04-23 23:18:42
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20091027000051KK01427