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问题 单项选择题

关于序贯试验的描述哪项是错误的。（）

A.可以不必预先估计样本大小

B.比一般的临床试验需要更多的样本

C.常用于病程短、见效快的疾病

D.可节约材料

E.连续分析资料，一旦结果达到统计学上的显著性即可停止试验

答案

参考答案：B

填空题

关系模式规范化过程中，若要求分解保持函数依赖，那么模式分解一定可以达到3NF，但不一定能达到【 】。
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单项选择题

A typical application of this (71) is ADSL. It is emerging as the technology for home-and small-office Internet connectivity. It provides either 1.5 Mb/s～8 Mb/s from the network to the user and 64 kb/s～512 kb/s in the reverse direction depending on the distance, 12000 or 18000 feet. The different speed for each direction gives it the (72) label. ADSL is designed to take advantage of the fact that video-on demand, telecommuting, and Internet access traffic are inherently asymmetrical. The user (73) a brief message up to the network and receives a ton of data coming back, either a movie or a piece of data download. Under such a scenario, low-speed traffic to the network is just fine. ADSL .delivers high (74) where you need it and only uses a single copper pair. Through multiplexing, it also reserves (75) of the bandwidth for POTS.

A．channel

B．computation

C．speed

D．bandwidth
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