the average of 6 observations is 13 . a new observation is included and the new average is decreased by 1 . the seventh observation is ?
let seventh observation = x . then , according to the question we have = > ( 78 + x ) / 7 = 12 = > x = 6 . hence , the seventh observation is 6 . answer : d
subtract(multiply(subtract(13, 1), add(6, 1)), multiply(13, 6))