AICとDICに関する非常にアヤしい自作メモ（その４への追記）

＊追記2010/04/27：すみません以下の記事ちょっと文脈的なところで適切でない部分がありました。詳しくはメモその５でフォローします。＊

今回は前回の追記的な短いメモになります。

改めてDICの元論文であるSpigelhalter et al. (2002)*1を読んでいたら、DIC概念の導入のところ（p603）で以下のようにハッキリ書いてありました*2。

Thus, by analogy with classical results described above, we propose a deviance information criterion DIC, defined as a classical estimate of fit, plus twice the effective number of parameters, to give

$DIC=D(\overline{\theta})+2p_{D}$ (36)
$=\overline{D}+p_{D}$ (37)

by definition of pD (10): equation (37) shows that DIC can also be considered as a Bayesian measure of fit or adequacy, penalized by an additional complexity term pD. From the results of section 3.2, we immediately see that in models with negligible prior information DIC will be approximately equivalent to Akaike's criterion.