Я считаю, что к настоящему времени должно быть ясно, что "подход CLT" дает правильный ответ.
Давайте точно определим, где «подход LLN» идет не так.
n−−√1/n−−√
P(1n−−√∑i=1nXi≤n−−√)=P(1n−−√∑i=1n(Xi−1)≤0)=P(1n∑i=1nXi≤1)
Zn=1n√∑ni=1(Xi−1)
P(1n−−√∑i=1nXi≤n−−√)=FZn(0)=FX¯n(1)
limn→∞FZn(0)=Φ(0)=1/2
X¯nX¯n
X¯n1
F1(x)={1x≥10x<1⟹F1(1)=1
... so limn→∞FX¯n(1)=F1(1)=1...
...and we just made our mistake. Why? Because, as @AlexR. answer noted, "convergence in distribution" covers only the points of continuity of the limiting distribution function. And 1 is a point of discontinuity for F1. This means that limn→∞FX¯n(1) may be equal to F1(1) but it may be not, without negating the "convergence in distribution to a constant" implication of the LLN.
And since from the CLT approach we know what the value of the limit must be (1/2). I do not know of a way to prove directly that limn→∞FX¯n(1)=1/2.
Did we learn anything new?
I did. The LLN asserts that
limn→∞P(|X¯n−1|⩽ε)=1for all ε>0
⟹limn→∞[P(1−ε<X¯n≤1)+P(1<X¯n≤1+ε)]=1
⟹limn→∞[P(X¯n≤1)+P(1<X¯n≤1+ε)]=1
The LLN does not say how is the probability allocated in the (1−ε,1+ε) interval. What I learned is that, in this class of convergence results, the probability is at the limit allocated equally on the two sides of the centerpoint of the collapsing interval.
The general statement here is, assume
Xn→pθ,h(n)(Xn−θ)→dD(0,V)
where D is some rv with distribution function FD. Then
limn→∞P[Xn≤θ]=limn→∞P[h(n)(Xn−θ)≤0]=FD(0)
...which may not be equal to Fθ(0) (the distribution function of the constant rv).
Also, this is a strong example that, when the distribution function of the limiting random variable has discontinuities, then "convergence in distribution to a random variable" may describe a situation where "the limiting distribution" may disagree with the "distribution of the limiting random variable" at the discontinuity points.
Strictly speaking, the limiting distribution for the continuity points is that of the constant random variable. For the discontinuity points we may be able to calculate the limiting probability, as "separate" entities.