單項(xiàng)選擇題要求估計(jì)量的數(shù)學(xué)期望等于被估計(jì)的總體參數(shù),這一標(biāo)準(zhǔn)被稱為()

A.一致性
B.無偏性
C.有效性
D.充分性


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1.單項(xiàng)選擇題變量x和y的相關(guān)系數(shù)的符號,取決于()

A.變量x的標(biāo)準(zhǔn)差
B.變量y的標(biāo)準(zhǔn)差
C.變量x和y兩個標(biāo)準(zhǔn)差的乘積
D.變量x和y的協(xié)方差

2.單項(xiàng)選擇題對于同一數(shù)據(jù),所計(jì)算出的平均差與標(biāo)準(zhǔn)差相比,通常有()

A.平均差大于標(biāo)準(zhǔn)差
B.平均差小于標(biāo)準(zhǔn)差
C.平均差等于標(biāo)準(zhǔn)差
D.二者關(guān)系不定

3.單項(xiàng)選擇題如果觀測變量的算術(shù)平均數(shù)>中位數(shù)>眾數(shù),則該觀測變量的次數(shù)分布是()

A.左偏分布
B.右偏分布
C.對稱分布
D.均勻分布

5.單項(xiàng)選擇題隨機(jī)變量的觀測值中出現(xiàn)次數(shù)最多的變量值是該變量的()

A.眾數(shù)
B.中位數(shù)
C.極值
D.均值

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