您提供的Wikipedia页面实际上并未使用术语“方差稳定化转换”。术语“方差稳定化变换”通常用于表示使随机变量的方差成为常数的变换。尽管在伯努利案中,这就是转型中正在发生的事情,但这并不完全是目标。目标是获得均匀的分布,而不仅仅是使方差稳定。
回想一下,使用Jeffreys Prior的主要目的之一是在变换下它是不变的。这意味着,如果您重新设置变量的参数,则先验不会改变。
1。
之前在此伯努利情况下杰弗里斯,因为你指出的那样,是一个测试。
p γ(γ )α 1(1/2,1/2)
pγ(γ)∝1γ(1−γ)−−−−−−−√.
用,我们可以找到θ的分布。首先让我们看θ = arcsin (√γ=sin2(θ)θ,并且由于0<γ<1,0<θ<π/2。回想一下,sin2(x)+cos2(x)=1。
˚F θ(X )θ=arcsin(γ−−√)0<γ<10<θ<π/2sin2(x)+cos2(x)=1
Fθ(x)fθ(x)=P(θ<x)=P(sin2(θ)<sin2(x))=P(γ<sin2(x))=Fγ(sin2(x))=dFγ(sin2(x)dx=2sin(x)cos(x)pγ(sin2(x))∝sin(x)cos(x)1sin2(x)(1−sin2(x))−−−−−−−−−−−−−−−−√=1.
Thus θ is the uniform distribution on (0,π/2). This is why the sin2(θ) transformation is used, so that the re-parametrization leads to a uniform distribution. The uniform distribution is now the Jeffreys prior on θ (since Jeffreys prior is invariant under transformation). This answers your first question.
2.
Often in Bayesian analysis one wants a uniform prior when there is not enough information or prior knowledge about the distribution of the parameter. Such a prior is also called a "diffuse prior" or "default prior". The idea is to not commit to any value in the parameter space more than other values. In such a case the posterior is then completely dependent on the data likelihood. Since,
q(θ|x)∝f(x|θ)f(θ)∝f(x|θ).
If the transformation is such that the transformed space is bounded, (like (0,π/2) in this example), then the uniform distribution will be proper. If the transformed space is unbounded, then the uniform prior will be improper, but often the resulting posterior will be proper. Although, one should always verify that this is the case.