某总体含有n个个体,现测得n个个体某定量指标的数值,即可求得总体均数值与总体标准差,

题型:单项选择题 A3/A4型题

问题:

某总体含有n个个体,现测得n个个体某定量指标的数值,即可求得总体均数值与总体标准差,计算总体标准差时,其自由度应该是()。

A.n-1

B.n

C.n-2

D.n+1

E.n+2

考点:输血技术(主管技师)主管技师相关专业知识主管技师相关专业知识题库
题型:单项选择题 A3/A4型题

下列计算正确的是  [ ]

A.2a﹣a=2

B.m6÷m2=m3  

C.x2008+x2008=2x2008

D.t2×t3=t6

题型:单项选择题 A3/A4型题

According to the US Geological Survey, about seven million earthquakes strike worldwide every year—but fortunately, only about 1500 of these are of a magnitude(震级) of 5 or greater on the Richter scale. Certain areas, such as California and Japan, are more prone to earthquakes than others. Although the chance of being caught in “The Big one” is remote, it’s wise to be prepared if you live in a region where earthquakes are common.

Educate your family about earthquakes before a big one strikes. For example, they need to know to take shelter in a doorway or under a strong object if indoors, and never to run outdoors if they are inside. If outside, they need to know to stay away from power lines and buildings where objects could fall.

Teach family members how to turn off gas or water lines or electrical power that may need to be shut off after a quake if severe damage occurs.

Develop a plan. Where will your family meet in the event of a disaster? What if some people are at work or school? How will you know if they are safe? Where will you all meet up?

Pack a preparedness kit(衣物装备) and keep it in a safe location. In a major earthquake, it’s possible that you won’t be able to get into your house. Keep supplies in your car trunk or an outside storage shed if possible. Pack whatever your family is likely to need, enough for three days to a week, including food, water, medication, first aid and personal hygiene supplies, flashlights, a portable radio, blankets, clothes and shoes, cash, or camp stove, candles, matches or lighters, and a whistle.

Consider earthquake insurance for your home if you live in an earthquake-prone area. Regular homeowner’s insurance doesn’t cover earthquake damage.

小题1:The underlined words “prone to ” in paragraph 1 can be replaced by___________.

A.likely to suffer

B.frequent to explore

C.regular to measure

D.impossible to experience小题2:According to the passage, if you are outside in an earthquake, you should_________.

A.stay where you are

B.hide under a big tree

C.avoid power lines

D.sit on the ground小题3: We can learn from the passage that_________.

A.about 1,500 earthquakes happen every year

B.people should store some clothes in their houses in advance

C.family members should meet in their home after an earthquake

D.people suffering earthquakes often should buy earthquake insurance小题4:What would be the best title for the passage?

A.How to Keep Safe in an Earthquake

B.How to Prepare for an Earthquake

C.Who Can Help Us After an Earthquake?

D.Where Is an Earthquake-prone Area?

题型:单项选择题 A3/A4型题

全口义齿修复后,由于垂直距离过高可能造成的影响是()

A.面形苍老

B.口角下垂,颏部前突

C.咀嚼时肌张力减低

D.加速牙槽骨吸收

E.以上都不是

题型:单项选择题 A3/A4型题

关于常量元素镁的生理功能,正确的是()。

A.机体缺镁时将会引起抽搐

B.镁是机体内硬组织的重要构成部分

C.镁主要存在于皮肤、毛发和指甲中

D.镁离子对维持体液的酸碱平衡起着重要作用

E.镁离子主要参与ATP的能量传递反应过程

题型:单项选择题 A3/A4型题

下列哪个不是主题学习网站的特点?()

A.共享开放

B.交互协作

C.交流便捷

D.资源共生

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