请教HLM中fixed effect 和 random effect 的问题

.微に酸袅袅

Hi， Kenny：

2 ]- U0 h) K2 c& T6 |% ~6 Ywhen we use HLM，there are some paper just report the fixed effect，while most time I use the random effect，so my question is when shall we use fixed or random effect and their difference？
! l$ t; Y( C- v, t5 S) x6 R, P
8 w; ^( \' d( U2 f6 }6 Aanother question is about the ground mean and the group mean， when we test the level 2 model， should we use group mean？can you give some guidance？

+ u3 [: Z! v6 ~' f0 GBest，
+ n$ i  K+ l8 e" X4 M9 |5 l  kKelly

Kenneth

Kelly，這是個給國內同學用的問題網站，麻煩用中文提問。謝謝。