问题 单项选择题

误码率是衡量一个通信系统传输可靠性的重要参数。对于一个实际的系统来说,______。

A.误码率越低越好

B.误码率越高越好

C.根据实际要求确定误码率

D.误码率高低关系不大

答案

参考答案:C

解析:
误码率是衡量一个通信系统传输可靠性的重要参数。误码率是指在数据传输系统中二进制位数被传错的概率P,它在数值上近似等于:P=Ne/N。式中:N为传输的二进制位总数,Ne为被传错的位数。对于一个实际的数据传输系统,要根据实际传输要求提出误码率,不能一味追求低误码率。计算机网络通信的误码率要求低于10-6~10-9。过低的误码率要求,将使得传输系统设备复杂而提高代价。
由于差错的出现具有随机性,在实际测量一个数据传输系统时,只有被测量的传输二进制码元数足够大,才能接近于系统真正的误码率值。

单项选择题
单项选择题

Remember the days when companies such as Microsoft and Mc-Kinsey took immense satisfaction from subjecting job candidates to mind-crunching strategy sessions If you thought that was rough, imagine an interview in which no amount of research or questioning of insiders will help. Imagine instead that all you can do is have a healthy breakfast, pick out your nicest suit, and hope for the best. In the new interview, they’re not just testing what you know. They’re also testing who you are.

It’s called the situational interview, and it’s quickly becoming a must in the job-seeking world. In the post-Enron culture of caution, corporations are focusing on an obvious insight: that a gold-plated resume and winning personality are about as accurate in determining job performance as Wall Street analysts are in picking stocks. Now, with shareholder scrutiny, hiring slowdowns, and expense-reducing, no manager can afford to hire the wrong person. Hundreds of companies are switching to the new methods. Whereas the conventional interview has been found to be only 7% accurate in predicting job performance, situational interviews deliver a rating of 54%—the most of any interviewing tool.

The situational technique’s superiority stems from its ability to trip up even the wittiest of interviewees. Of course, every applicant must display a healthy dose of occupational know-how, but behavior and ethical backbone play a big role. For example, a prospective analyst at a Wall Street bank might have to face, say, a customer with an account argument. It’s not happening on paper, but in real time—with managers and experts watching nearby. The interviewer plays the role of a fierce customer on the phone, angry about money lost when a trade wasn’t executed on time. It’s set up as an obvious mistake on the banker’s part.

Interviewers watch the candidates’ reactions: how they process the complex account information, their ability to talk the client down, what their body language displays about their own shortcomings, and which words they choose. In this instance, not being honest about the mistake or showing anger or frustration—no matter how glowing your resume—means you’re out.

Behavioral interviews are also being rounded out by other tools that, until recently, had been reserved for elite hires. Personality-testing outfit Caliper, for example, which probes candidates for emotional-intelligence skills and job ability, has seen its business jump 20% this year.

Clearly, the new interview isn’t without its drawbacks. Companies run the risk of arousing hostility in candidates, who may feel as if some line has been crossed into personal territory. Moreover, sortie companies worry about the fairness of personality tests. They have to make sure there are no inherent gender or racial biases in the test.

The new interview is widely adopted because of its ().

A.efficiency in selecting the fittest brains

B.insight into the interviewee’s character

C.accuracy in testing working experience

D.exactness in assessing performing skills