设总体X~N(μ,σ2),已知样本容量n=24,样本方差s2=12.5227.求总体标准差σ大于3的概率.
∵(n-1)s2/σ2~X2(n-1) ∴P{σ﹥3}=P{σ2﹥9}=P{(n-1)s2/σ2﹤[(n-1)s2/9]} =1-P{(n-1)s2/σ2≥[(n-1)s2/9]} =1-P{x2(23)≥32} =1-0.1=0.9
设总体X~N(μ,σ2),已知样本容量n=24,样本方差s2=12.5227.求总体标准差σ大于3的概率.
∵(n-1)s2/σ2~X2(n-1) ∴P{σ﹥3}=P{σ2﹥9}=P{(n-1)s2/σ2﹤[(n-1)s2/9]} =1-P{(n-1)s2/σ2≥[(n-1)s2/9]} =1-P{x2(23)≥32} =1-0.1=0.9