... ó trung bình và phng sai ca L c tính nh sau ( ) ( ) ( ) ( )nLM LMLMnL LLMLMn21n21=+++=+++= ( ) ( ) ( ) ( )nnLDLDLDnLLLDLD22n21n21σ=+++=+++= ... P/,+/"O 21n1j2jLL1n1LS−−== )() ( T+/#,+/O ( )[ ]3n1j3j3LSLL2n1nnL )( ) )(( )( =−−−=α ... '+"8/"3.+%)',)*'6+,#&)+#)+#f'#.*77#""#?598,+/&)0'-)+)O =iiiLPLM )( N)*O −=σi2ii2LMLPL ) ]([ )( P/,+/"O )() ( LL2σ=σ T+/#+#+O )( )( LMLCVσ= ...