P{X≤0}= φ[(0-2)/3]=φ[-2/3]=1-φ[2/3]=1-0.74=0.26
P{|X|≤1.5}=P{-1.5≤x≤1.5}
P{x≤1.5}=φ[(1.5-2)/3]=φ[-1/6]=1-0.56=0.44
P{x≤-1.5}=φ[(-1.5-2)/3]=φ[-3.5/3]=1-φ[3.5/3]=1-0.87=0.13
所以P{|X|≤1.5}=P{-1.5≤x≤1.5}=P{x≤1.5}-P{x≤-1.5}=0.44-0.13=0.31
P{X≤0}= φ[(0-2)/3]=φ[-2/3]=1-φ[2/3]=1-0.74=0.26
P{|X|≤1.5}=P{-1.5≤x≤1.5}
P{x≤1.5}=φ[(1.5-2)/3]=φ[-1/6]=1-0.56=0.44
P{x≤-1.5}=φ[(-1.5-2)/3]=φ[-3.5/3]=1-φ[3.5/3]=1-0.87=0.13
所以P{|X|≤1.5}=P{-1.5≤x≤1.5}=P{x≤1.5}-P{x≤-1.5}=0.44-0.13=0.31