using excel for the calculations

download Workbook 4.9.+Confidence+intervals+Two+neans.+independent+samples+(Part+2)_excercise

SHEET CI, indep, var unkwn
                           NY      LA
Sample mean $3.94   $3.25    ***MEAN FORMULA*** =AVERAGE(B10:B19) | =AVERAGE(C10:C17)
Sample std    $0.18   $0.27    ***Std. dev formula***  =STDEV.S(B10:B19) | =STDEV.S(C10:C17)
Sample size       10        8

***Pooled variance formula*** =(F11*F11*9+G11*G11*7)/16

what is being calculated inside the formula =               (NY*NY*9+LA*LA*7)/16
Column Row #s being pulled may differ in your sheet =(F11*F11*9+G11*G11*7)/16
the actual numbers being pulled =                             (3.94*3.94*9+3.25*3.25*7)/16

***Pooled std formula*** =SQRT(F14)
=SQRT of Pooled variance
Squared root of 0.05 equals Pooled variance = 0.22