=? 
举一反三
- 设总体X～N(μ,σ^2),μ和σ是未知参数。为估计参数σ^2的置信区间，应选T=____________作为枢轴变量,并且T服从______。? <img src="http://img2.ph.126.net/SHUrsWncVzw3TbqMT630Ug==/6632510324955921443.png" /><br />|<img src="http://img2.ph.126.net/I5VmIURcDfhDZIPIQy5JZw==/6632334403095483329.png" />|<img src="http://img0.ph.126.net/v1kDLV9rE4i9IWRPugufXQ==/6632404771839652521.png" />|<img src="http://img0.ph.126.net/sQOy3VhGtuk-bcM7dsC3kQ==/6632272830444326010.png" />
- <img src="http://img2.ph.126.net/qowvyGJmU71A6UIpMtWkYw==/6619531689700953755.jpg" />? <img src="http://img2.ph.126.net/un3GDHXLxtcRiMEcP1z7yg==/6619072093840546265.jpg" />|<img src="http://img2.ph.126.net/IZ9fF3KQHcgJNZoygylhHQ==/6630845664350440712.jpg" />|<img src="http://img2.ph.126.net/_iw_TRTbgBcFfQ9EIzN3YA==/6619139164049839979.jpg" />|<img src="http://img2.ph.126.net/Tehi0XAX-FVa8la7PAFlnw==/2435602973495420798.jpg" />
- n位触发器构成的扭环形计数器，其无效状态数有( )个。? <img src="http://img1.ph.126.net/syawN86lkJeyXf8emf2enw==/6630087001327300267.png" />|<img src="http://img2.ph.126.net/0JBcfdqdyUjt5-uTh7cmUQ==/4886405595797893661.png" />|<img src="http://img2.ph.126.net/qBQGx0Z9T_pt4PZJc8Nn7g==/6608560762678510607.png" />|<img src="http://img0.ph.126.net/elyGxaiPbD815O67sULOnQ==/1876312194853825038.png" />
- <img src="http://img1.ph.126.net/xRWXQUfZJwmSXkQiZ0l2HQ==/3826089358528721080.jpg" />? <img src="http://img2.ph.126.net/QX-jBzzFTrwpTjQkcBtfcg==/2449958197307439176.jpg" />|<img src="http://img0.ph.126.net/3XApesgU0Iga8L5Tkm0YXg==/6630324495838409649.jpg" />|<img src="http://img2.ph.126.net/sPsiWYSStdIbrCUcsMBK9A==/3114802092298176869.jpg" />|<img src="http://img1.ph.126.net/y-FdOVmaocQvOIOXtXTxEw==/662592095194801258.jpg" />
- 在一条两端固定且长度等于L的弦线上形成驻波，波长必须要等于 未知类型：{'options': ['[img src="http://img2.ph.126.net/OivZqWKlnBUdqXnie-awkQ==/6631282170465999716.png"]，n是大于0的整数', '[img src="http://img2.ph.126.net/kkh6Hqq0EqfnoqUSzK8JOA==/4833206825199367892.png"]，n是大于0的整数', '[img src="http://img1.ph.126.net/E1oRuo-fffSF5_ey56Qzsw==/4833206825199367921.png"]，n是大于0的整数', '[img src="http://img2.ph.126.net/FX-70jFWzObrUJycm8GWSg==/4863606122684719385.png"]，n是大于0的整数'], 'type': 102}