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Q21Section A (Section A)21 of 60

Limit of chi-square tail probabilities

Let {Xn}n≥1\{X_n\}_{n\ge1} be a sequence of independent random variables with XnX_n having the probability density function

fn(x)={12n/2Γ(n2)e−x2x(n2−1),x>0, 0,otherwise.f_n(x)=\begin{cases}\dfrac1{2^{n/2}\Gamma\left(\frac n2\right)}e^{-\frac x2}x^{\left(\frac n2-1\right)}, & x>0,\ 0, & \text{otherwise.}\end{cases}

Then lim⁡n→∞[P(Xn>34n)+P(Xn>n+22n)]\lim_{n\to\infty}\left[P\left(X_n>\dfrac34n\right)+P\left(X_n>n+2\sqrt{2n}\right)\right] equals

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