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让我们据span class="katex"> X据/span>和据span class="katex"> y据/span>具有联合概率密度功能:据span class="katex-display"> F据/span>(据/span>X.据/span>那据/span>y据/span>)据/span>=据/span>4.据/span>9.据/span>1据/span>X.据/span>y据/span>对于据span class="katex"> 0.据/span>≤.据/span>X.据/span>≤.据/span>2据/span>和据span class="katex"> 0.据/span>≤.据/span>y据/span>≤.据/span>7.据/span>。据/span>找到预期的价值据span class="katex"> 3.据/span>X据/span>。据/span>
让我们据span class="katex"> X据/span>和据span class="katex"> y据/span>具有联合概率密度功能:据span class="katex-display"> F据/span>(据/span>X.据/span>那据/span>y据/span>)据/span>=据/span>K.据/span>(据/span>X.据/span>+据/span>y据/span>)据/span>对于据span class="katex"> 0.据/span>≤.据/span>X.据/span>≤.据/span>1据/span>0.据/span>和据span class="katex"> 0.据/span>≤.据/span>y据/span>≤.据/span>1据/span>那据/span>在哪里据span class="katex"> K.据/span>是一个常数。找到边际概率据span class="katex"> P.据/span>(据/span>1据/span>≤.据/span>X据/span>≤.据/span>2据/span>)据/span>。据/span>
让我们据span class="katex"> X据/span>和据span class="katex"> y据/span>具有联合概率密度功能:据span class="katex-display"> F据/span>(据/span>X.据/span>那据/span>y据/span>)据/span>=据/span>K.据/span>对于据span class="katex"> 0.据/span>≤.据/span>X.据/span>≤.据/span>5.据/span>和据span class="katex"> 0.据/span>≤.据/span>y据/span>≤.据/span>8.据/span>那据/span>在哪里据span class="katex"> K.据/span>是一个常数。找到之间的协方差据span class="katex"> X据/span>和据span class="katex"> y据/span>。据/span>
让我们据span class="katex"> X据/span>和据span class="katex"> y据/span>具有联合概率密度功能:据span class="katex-display"> F据/span>(据/span>X.据/span>那据/span>y据/span>)据/span>=据/span>K.据/span>X.据/span>y据/span>对于据span class="katex"> 0.据/span>≤.据/span>X.据/span>≤.据/span>4.据/span>和据span class="katex"> 0.据/span>≤.据/span>y据/span>≤.据/span>3.据/span>那据/span>在哪里据span class="katex"> K.据/span>是一个常数。找据span class="katex"> P.据/span>(据/span>X据/span>据据/span>y据/span>)据/span>。据/span>
以下哪项不能成为两个连续随机变量的联合概率密度函数据span class="katex"> X据/span>和据span class="katex"> y据/span>还是据/span>
(a):据/strong> F据/span>(据/span>X.据/span>那据/span>y据/span>)据/span>=据/span>1据/span>对于据span class="katex"> 0.据/span>≤.据/span>X.据/span>那据/span>y据/span>≤.据/span>1据/span>。据/span>
(b):据/strong> F据/span>(据/span>X.据/span>那据/span>y据/span>)据/span>=据/span>X.据/span>+据/span>y据/span>对于据span class="katex"> 0.据/span>≤.据/span>X.据/span>那据/span>y据/span>≤.据/span>1据/span>。据/span>
(C):据/strong> F据/span>(据/span>X.据/span>那据/span>y据/span>)据/span>=据/span>X.据/span>y据/span>对于据span class="katex"> 0.据/span>≤.据/span>X.据/span>那据/span>y据/span>≤.据/span>1据/span>。据/span>
(d):据/strong> F据/span>(据/span>X.据/span>那据/span>y据/span>)据/span>=据/span>E.据/span>X.据/span>+据/span>y据/span>对于据span class="katex"> 0.据/span>≤.据/span>X.据/span>那据/span>y据/span>≤.据/span>LN.据/span>2据/span>。据/span>
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