if x is the first group of cds and y is the second group then
the mean of the total group is
You know that
You say you calculated xbar already (although i have not seen and dont follow that method). you are given ybar.
the price of a CD is denoted by $x. for 60 CDs bought in different stores it is found that sigma(x-12) = 53.40. Calculate the mean price of these CDs. The mean price of a further 40 CDs is found to be $11.64. Find the mean price of the 100 CDs.
The first problem was easy, divide 53.40 by 60 and add 12. BUt with the second one i don't know what method to use i know it must be more complicated than adding the two means and dividing by two