Question: Battery Voltage. Two brands of batteries were tested and their voltage is compared. The data follow. Find the 95% confidence interval of the true difference in the means. Assume that both variables are normally distributed.

Brand X Brand Y

X1 = 9.2 volts X2 = 8.8 volts

\({{\sigma }_{1}}\) = 0.3 volt \({{\sigma }_{2}}\) = 0.1 volt

n1 = 27 n2 = 30