题库搜索>问题求解PS-15609
建议使用官方纸质指南，查看对照完整题目
【OG20-P169-151题】
For each student in a certain class, a teacher adjusted the student’s test score using the formula y = 0.8x + 20, where x is the student’s original test score and y is the student’s adjusted test score. If the standard deviation of the original test scores of the students in the class was 20, what was the standard deviation of the adjusted test scores of the students in the class?
分析A选项
分析B选项
分析C选项
分析D选项
分析E选项
我有更好的解析 
暂无雷哥网文字解析
答案 B
【解析】
序列中每一个数同时加上一个常数，标准差、保持不变！ 序列中每一个数乘以一个常数X，则标准差扩大X倍。 所以，修正后的标准差应该是20×0.8=16。
【知识补充】
1、样本同时加上一个数，方差标准差不变，均值加上这个数。
2、样本同时乘以一个数，方差乘以该数的平方，标准差，均值乘以这个数。
学霸丞哥
D(x)=400 D(0.8x+20)=0.64D(x) D(x)是方差，标准差开平方
0
0
回复
2019-09-12 09:11:10
730以上
贴一个其它网站过来的解释（特别好的解释） 记住： 序列中每一个数都加上一个常数，标准差、方差保持不变！ 序列中每一个数乘以一个常数X，则标准差扩大X倍，方差扩大X²倍。 自己拿1，2，3，4，5套公式试试。记住就好 所以这题不管+号后面，就管乘积0.8，修正后的标准差应该是20*0.8=16
17
0
回复
2018-01-15 14:50:41
lealuo回复730以上
谢谢
0
0
回复
2018-03-08 23:58:06
冲鸭冲鸭冲鸭回复730以上
感谢！
0
0
回复
2018-10-15 04:10:04
700吧回复730以上
感谢！
0
0
回复
2018-11-30 20:12:29
科目：
问题求解PS
来源：
OG18新题
题目信息1m24s
平均耗时
70%
平均正确率
该题由网友iw8rh35y提供
点击上传问题求解PS -16754
【OG20-P148-15题】Over the past 7 weeks, the Smith family had weekly grocery bills of $74, $69 ,$64, $79, $64, $84, and $77. What was the Smiths’ average(arithmetic mean) weekly grocery bill over the 7-week period?
问题求解PS -16747
【OG20-P163-114题】The table shows partial results of a survey in which consumers were asked to indicate which one of six promotional techniques most influenced their decision to buy a new food product .Of those consumers who indicated one of the four techniques listed ,what fraction i...
问题求解PS -16745
【OG20-P167-134题】10 ，4 ，26 ，16What is the median of the number shown ?
问题求解PS -16744
【OG20-P148-17题】During a recent storm ,9 neighborhoods experienced power failures of durations 34,29,27,46,18,25,12,35,and 16 minutes ,respectively .For these 9 neighborhoods ,what was the median duration ,in minutes ,of the power failures ?
问题求解PS -16740
【OG20-P146-3题】During a trip that they took together ,Carmen ,Juan ,Maria ,and Rafael drove an average (arithmetic mean )of 80 miles each. Carmen drove 72 miles ,Juan drove 78 miles ,and Maria drove 83 miles .How may miles did Rafael drive ?
问题求解PS -16754
【OG20-P148-15题】Over the past 7 weeks, the Smith family had weekly grocery bills of $74, $69 ,$64, $79, $64, $84, and $77. What was the Smiths’ average(arithmetic mean) weekly grocery bill over the 7-week period?
问题求解PS -16747
【OG20-P163-114题】The table shows partial results of a survey in which consumers were asked to indicate which one of six promotional techniques most influenced their decision to buy a new food product .Of those consumers who indicated one of the four techniques listed ,what fraction i...
问题求解PS -16745
【OG20-P167-134题】10 ，4 ，26 ，16What is the median of the number shown ?
问题求解PS -16744
【OG20-P148-17题】During a recent storm ,9 neighborhoods experienced power failures of durations 34,29,27,46,18,25,12,35,and 16 minutes ,respectively .For these 9 neighborhoods ,what was the median duration ,in minutes ,of the power failures ?
问题求解PS -16740
【OG20-P146-3题】During a trip that they took together ,Carmen ,Juan ,Maria ,and Rafael drove an average (arithmetic mean )of 80 miles each. Carmen drove 72 miles ,Juan drove 78 miles ,and Maria drove 83 miles .How may miles did Rafael drive ?
分享
周末、晚班滚动开班 
24+35+35+6课时 
