Kamandirian statistik: Béda antarrépisi

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Baris ka-47:
:var(''X'' + ''Y'') = var(''X'') + var(''Y'').
 
IfLamun ''X'' andjeung ''Y'' are independentbebas, the [[covariancekovarian]] cov(''X'',''Y'') issarua jeung zeronol; otherwisedina wehal wouldsejen havemibanda
 
:var(''X'' + ''Y'') = var(''X'') + var(''Y'') + 2 cov(''X'', ''Y'').
 
(''Pernyataan'' sabalikna yen lamun dua variabel bebas mangka kovarian-na sarua jeung nol ngarupakeun hal nu teu bener. Tempo [[uncorrelated|taya hubungan]].)
(The converse of the proposition that if two random variables are independent then their covariance is 0 is not true. See [[uncorrelated]].)
 
Furthermore, if ''X'' and ''Y'' are independent and have [[probability density function|probability densities]] ''f''<sub>''X''</sub>(''x'') and ''f''<sub>''Y''</sub>(''y''), then the combined random variable (''X'',''Y'') has a joint density