sample means and b) both variances. Decide c) which brand battery lasts longer and d) which brand has the more consistent lifetime.
Brand A: $72,67,65,71,72$
Brand $\mathrm{B}: 70,71,72,70,72$

Step 1 ：Given the battery life data for Brand A: 72, 67, 65, 71, 72 and Brand B: 70, 71, 72, 70, 72.

Step 2 ：Calculate the sample mean for both brands. The sample mean is the sum of all the data points divided by the number of data points.

Step 3 ：For Brand A, the mean is \(\frac{72+67+65+71+72}{5} = 69.4\)

Step 4 ：For Brand B, the mean is \(\frac{70+71+72+70+72}{5} = 71.0\)

Step 5 ：Next, calculate the variance for both brands. The variance is a measure of how spread out the numbers in the data set are. It is calculated by taking the average of the squared differences from the mean.

Step 6 ：For Brand A, the variance is \(\frac{(72-69.4)^2+(67-69.4)^2+(65-69.4)^2+(71-69.4)^2+(72-69.4)^2}{5} = 10.3\)

Step 7 ：For Brand B, the variance is \(\frac{(70-71)^2+(71-71)^2+(72-71)^2+(70-71)^2+(72-71)^2}{5} = 1.0\)

Step 8 ：Based on the calculations, Brand B has a higher mean battery life and a lower variance, indicating that it lasts longer on average and has a more consistent lifetime.

Step 9 ：Final Answer: The brand that lasts longer is Brand B with a mean battery life of \(\boxed{71.0}\) hours. The brand with the more consistent lifetime is also Brand B with a variance of \(\boxed{1.0}\) hours.