单选题 A sample of employees were tested on data—entry skills for one hour，and the number of errors (x) they made and the percent of employees (p) making x errors were recorded as follows．
Number
of Errors
x		 Percent of
Employees
p
0
1
2
3
4
5
6 or more		 2%
5%
10%
24%
17%
20%
22%


单选题 If those employees who made 6 or more errors were removed from the sample and an employee were selected at random from those remaining，what is the probability that the employee selected made no errors?
【正确答案】 C
【答案解析】若把犯6个或6个以上错误的职员移出样本，并且从剩余职员中随机挑出一名职员，问该职员未犯任何错误的概率是多少?
由袁可知，有6个或6个以上错误的职员的百分比为22%，移走这一部分后，剩余78%的职员中，不犯错误的职员占2%，所以其概率为：
[*]
单选题 What was the median number of errors in the sample?
A. 3
B. 3.5
C. 4
D. 4.5
E. It cannot be determined from the information given．
【正确答案】 C
【答案解析】样本中犯错误次数的中数是多少?
样本中犯错误次数的中数，指样本中中间一个人所犯的错误。考生可以设该样本中共有100人，因为100是偶数，所以样本中犯错误次数的中数为第50个人和第51个人犯错误次数的和除以2。根据表格中的数据有：犯0个错误的人有2个，犯1个错误的人有5个，犯2个错误的人有10个，犯3个错误的人有24个，犯4个错误人的有17个，那么按错误数目排序的第50人和51人均有4个错误，所以中数为4。
一个测试职员数据输入技巧的样本，在一小时中犯错误的次数(x)和犯该错误次数的职员的百分比(P)记录如左：