The mean voltage and standard deviation of 10 batteries from each manufacturer were measured. The results are summarized in the following table.

Manufacturer	Sample mean voltage (millivolts)	Population standard deviation(millivolts)
A	171	2
B	169	4

What type of hypothesis test should be performed? Left-tailed z-test, paired t-test, two-tailed z-test, unpaired t-test

What is the test statistic?

What is the number of degrees of freedom?

Does sufficient evidence exist to support the claim that the voltage of the batteries made by the two manufacturers is different at the =0.05 significance level? Yes or No