某次考试的考生成绩服从正态分布，从中随机地抽取 36 位考生的成绩，算得平均成 绩为 
分，标准差为 15 分。 则在显著性水平 
下，可以认为这次考试全体考生的平均成绩为 70 分( )
分，标准差为 15 分。 则在显著性水平 下，可以认为这次考试全体考生的平均成绩为 70 分( )
举一反三
- 设某次考试的考生成绩服从正态分布,从中随机地取 36 位考生的成绩,算得平均成绩为 66.5 分,标准差为 15 分,问在显著水平 0.05 下, 是否可以认为这次考试全体考生的平均成绩为 70 分?
- 下列方程为伯努利方程的是（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/0622f56257874ab19e680d587fd8a4fc.png"> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/5ce3fc785b724e3da7d07b8d6a0ecaf3.png"> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/ab3de1c35e9e419fa301a33bddd5ee0c.png">+<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/2c226f2daecf40448b08c3b26a4db60e.png"> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/88be95dd74814341a1894f32f073b9ec.png"><img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/00fbcbc7c3574f94934fa3adc8843ccf.png">
- 直线<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/64709df03a7b45ebbc6d752183b8f22e.png" />与直线<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/5ca5aa44859c42ddaa3207626d2b9537.png" />的公垂线方程为（ ） A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/a4c463fa2c3f49df9d7f2bb2e9fc4030.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/627b64a33e944efcba416aea0f40dc76.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/966e8a14e6754060b800dff88721784a.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/f8f41491de204a9eb3fb306208c3b08a.png" />
- 开环系统频率特性<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/d87c0f560f1542028a3602b52456fae0.png" />，当<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/c0f50539680f40a784c2a0d803f0f5d7.png" />时，其频率特性相角<img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/ff41a81bec7c421c8178de199c438e05.png" />（ ）。 A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/589b5e2ab46b459882a2824ff9567c36.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/370b677492de485ca61114324b5d00fe.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/95723a2a938f4944a98b18d89f607986.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/c08161009369424f9a3510d7c77d9943.png" />
- 设r为接收机输入端信噪比，2DPSK调制系统差分解调的误码率计算公式为( ) A: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/917a2c41f1d543589c93d38fb2554b7a.png" /> B: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/056233e9bd974877b6c99f2faf89b690.png" /> C: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/39e80494876e4b88867029f0308bb53f.png" /> D: <img src="https://image.zhihuishu.com/zhs/doctrans/docx2html/202108/d66948e876314f03a167a8dd40aae4b7.png" />