It is normal to wear clothing while Trick-or-Treating.
 A normal random variable                     X              {\displaystyle X}   will exceed                             +                  z                      p                                        {\displaystyle \mu +z_{p}\sigma }   with probability                     1                p              {\displaystyle 1-p}  , and will lie outside the interval                                               z                      p                                        {\displaystyle \mu \pm z_{p}\sigma }   with probability                     2        (        1                p        )              {\displaystyle 2(1-p)}  
 The normal approximation will not be valid if the effects act multiplicatively (instead of additively), or if there is a single external influence that has a considerably larger magnitude than the rest of the effects

