我
=100,方差
=25的正态分布，现采用一种新工艺生产该种元件，并随机抽取25个元件，测得样本均值
=105,从生产情况看，寿命波动无变化，试判断采用新工艺生产的元件平均寿命较以往有无显著变化.(a=0.05,
。
。
- 8
-
为样本，
则
=______。- 10
-
X服从参数
=______。
则D(X)=______。- 15
-
,则常数c等于()- A.1
- B.-1
- C.2
- D.-2
为来自总体X的样本,
为样本均值，则样本方差
=() - A.<img src="//img1.yqda.net/question-name/ae/87ad499ee1c122b29b1dc19bf737e9.png" width="211" height="72"/>
- B.<img src="//img1.yqda.net/question-name/74/4148088ebe7d6635cc0d44122535b7.png" width="261" height="70"/>
- C.<img src="//img1.yqda.net/question-name/5f/df702d66317f9b56415f4559f3f174.png" width="254" height="81"/>
- D.<img src="//img1.yqda.net/question-name/22/8985f01c83552b16e1000ee6543ecd.png" width="256" height="71"/>
- 18
-
- A.<img src="//img1.yqda.net/question-name/f2/98e423c0115445fe52a5674c5b340d.png" width="26" height="26"/>是E(X)的无偏估计
- B.<img src="//img1.yqda.net/question-name/f2/98e423c0115445fe52a5674c5b340d.png" width="26" height="26" />是D（X）的无偏估计
- C.<img src="//img1.yqda.net/question-name/f2/98e423c0115445fe52a5674c5b340d.png" width="26" height="26" />是E(X)的矩估计
- D.<img src="//img1.yqda.net/question-name/f2/98e423c0115445fe52a5674c5b340d.png" width="26" height="26" />是<img src="//img1.yqda.net/question-name/c5/b90aa32f51b0c1665b31a31a5b6572.png" width="35" height="39"/>的无偏估计
- A.0.5
- B.0.33
- C.0.66
- D.0.8
为来自总体X的样本(n>1)，且D(X)=
，则- A.<img src="//img1.yqda.net/question-name/94/f6ea69bf6b41b3f7f9c2ef4c13127c.png" width="245" height="72"/>
- B.<img src="//img1.yqda.net/question-name/98/38fd0a10df321e09f5c5daadccff65.png" width="195" height="70"/>
- C.<img src="//img1.yqda.net/question-name/f3/3e7b9878344aaa27eb52742902affe.png" width="240" height="68"/>
- D.<img src="//img1.yqda.net/question-name/0a/9e417792fce603feb48df90a60196f.png" width="248" height="70"/>
)，(
=()- A.<img src="//img1.yqda.net/question-name/2c/51c84797083b6d100bd8234fc3b5e3.png" width="15" height="30" />
- B.<img src="//img1.yqda.net/question-name/b6/26663af424cb19a8fdc39b2ade3ebd.png" width="12" height="46"/>
- C.1
- D.<img src="//img1.yqda.net/question-name/51/8a658989502c001924c25a69fa808f.png" width="17" height="24"/>
则
()- A.13.4
- B.13.3
- C.13.2
- D.8.4
则常数c=()- A.1
- B.2
- C.3
- D.4
- 24
-
- A.<img src="//img1.yqda.net/question-name/b5/f97cd3e2c5f2cbe5454355545a5f00.png" width="198" height="44"/>
- B.<img src="//img1.yqda.net/question-name/d6/45de52ec2c7e38d9eca5594f3f7aae.png" width="188" height="44"/>
- C.<img src="//img1.yqda.net/question-name/89/fb3b3da65293233525b40dc1b62564.png" width="191" height="44"/>
- D.<img src="//img1.yqda.net/question-name/7d/d121636fee4e13ce173949c43f8a4d.png" width="191" height="44"/>
- A.X与Y独立
- B.X与Y不相关
- C.D(XY)=D(X)D(Y)
- D.D(X-Y)=D(X)-D(Y)
