在抽样研究中，增加样本含量的目的是（） A.缩小均数 B.缩小变异系数 C.缩小样本

青年附睾肿块，考虑为

A．子痈
B．子痰
C．阴茎痰核
D．淋浊
E．精癃

写出一个具体的y随x的增大而减小的一次函数解析式（    ）。

单管系统与双管系统比较，单管系统在各层散热器的进出水温度（）

A、是不相同的

B、是相同的

C、越在下层，进水温度越高

D、都有可能

《入境货物报检单》的编号由检验检疫报检受理人员填写，其中，第8、9位是( )。

A．检验检疫机构代码
B．报检类代码
C．年代码
D．流水号

There is a great deal of geographical variation in the frequency of many surgical procedures—up to tenfold variation per hundred thousand between different areas in the numbers of hysterectomies, prostatectomies, and tonsillectomies. To support a conclusion that much of the variation is due to unnecessary surgical procedures, it would be most important to establish which of the following

A．A local board of review at each hospital examines the records of every operation to determine whether the surgical procedure was necessary.

B．The variation is unrelated to factors (other than the surgical procedures themselves) that influence the incidence of diseases for which surgery might be considered.

C．There are several categories of surgical procedure (other than hysterectomies, prostatectomies, and tonsillectomies) that are often performed unnecessarily.

D．For certain surgical procedures, it is difficult to determine after the operation whether the procedures were necessary or whether alternative treatment would have succeeded.

E．(E) With respect to how often they are performed unnecessarily, hysterectomies, prostatectomies, and tonsillectomies are representative of surgical procedures in general.