[求助]SAS BASE 的一道题

是 否 +2 论坛币

k人 参与回答

经管之家送您一份

应届毕业生专属福利!

求职就业群

赵安豆老师微信：zhaoandou666

经管之家联合CDA

送您一个全额奖学金名额~ !

立即领取

感谢您参与论坛问题回答

经管之家送您两个论坛币！

+2 论坛币

在准备SAS BASE的考试, 做123时遇到的这道题, 怎么想都想不通为什么答案是B而不是C. 请高手指点一下.

A SAS PRINT procedure output of the WORK.LEVELS data set is listed
> below:
> Obs name level
> 1 Frank 1
> 2 Joan 2
> 3 Sui 2
> 4 Jose 3
> 5 Burt 4
> 6 Kelly .
> 7 Juan 1
> The following SAS program is submitted:
> data work.expertise;
> set work.levels;
> if level = . then
> expertise = 'Unknown';
> else if level = 1 then
> expertise = 'Low';
> else if level = 2 or 3 then
> expertise = 'Medium';
> else
> expertise = 'High';
> run;
> Which of the following values does the variable EXPERTISE contain?
> A. Low, Medium, and High only
> B. Low, Medium, and Unknown only
> C. Low, Medium, High, and Unknown only
> D. Low, Medium, High, Unknown, and ' ' (missing character value)
> Answer: B

扫码加我 拉你入群

请注明：姓名-公司-职位

以便审核进群资格，未注明则拒绝

分享0 收藏0 回帖

关键词：SAS base Base following Character Procedure 求助 SAS Base

else if level = 2 or 3  then
should be
else if level = 2 or level= 3  then

[此贴子已经被作者于2009-3-6 4:44:32编辑过]

这是考阅读，不是考编程

这道题考了两点：
１。if 语句中的 or 和 and 的前后应该是两个条件。每一个条件为 true 时 return １， 为 false 时 return ０。
 if level = 2 or 3 then 语句中 or 后面 的 ３ is a constant and >0 所以 always 为 ture。

２。 if， else if 中条件判断的次序。
 if level = . then  expertise = 'Unknown';
 else if level = 1 then expertise = 'Low';
 else if level = 2 or 3 then  expertise = 'Medium';
试着把上面的else if 的次序换一下，再看看结果就明白了。
 if level = . then  expertise = 'Unknown';
 else if level = 2 or 3 then  expertise = 'Medium';
 else if level ＝ １ then expertise = 'Low';

[此贴子已经被作者于2009-3-6 13:34:58编辑过]

"if level=2 or 3" means if level=2 or if 3, so this condition is always true, anything comes after it and does not meet all the previous conditions will be resolved to 'Medium'. If you put it on top you will only get one result for all the observations: 'Medium'.