Fear of mice avoid a mouse, showing there may be some basis for this belief. It is not known why elephants should react in this way, though there are several theories. Regardless, elephantine murophobia remains the basis of various jokes and metaphors. The classical board game Dou Shou Qi has the Rat kill an Elephant: as multiple editions of the rule book mentions that the Rat would crawl into the Elephant's ears to gnaw into its brain: but this is considered to be a folk tale. Gertrude of Nivelles is the patron saint of murophobia, and is also invoked against rats and mice
Abnormal return where: AR - abnormal return for firm i on day t R - actual return for firm i on day t E(R) – expected return for firm i on day t A common practice is to standardise the abnormal returns with the use of the following formula: formula_3 where: SAR - standardised abnormal returns SD – standard deviation of the abnormal returns The SD is calculated with the use of the following formula: formula_4 where: S – the residual variance for firm i, R – the return on the stock market index on day t, R – the average return