Pengukuran potensi kerugian indeks bursa saham dengan pendekatan VaR volatilitas EWMA dan GARCH (studi pada 8 indeks periode Agustus 2007 Desember 2012) = Measurement of loss potential for stock market index by using var EWMA and GARCH volatility (study of 8 indices with the period of August 2007 December 2012)