(Solved): A consumer advocate researches the length of life between two brands of refrigerators, Brand A and ...

A consumer advocate researches the length of life between two brands of refrigerators, Brand A and Brand B. He collects data (measured in years) on the longevity of 40 refrigerators for Brand $A$ and repeats the sampling for Brand B. A portion of the data is shown in the accompanying table. (You may find it useful to reference the appropriate table: ztable or ttable) Click here for the Excel Data File Assume that ${?}_1$ is the mean longevity for Brand $A$ and ${?}_2$ is the mean longevity for Brand $B$. a. Select the competing hypotheses to test whether the average length of life differs between the two brands. $\begin{array}{l}{H}_0:{?}_1?{?}_2=0;H_A:{?}_1?{?}_2?0\\ H_0:{?}_1?{?}_2?0;H_A:{?}_1?{?}_2<0\\ H_0:{?}_1?{?}_2?0;H_A:{?}_1?{?}_2>0\end{array}$ b-1. Calculate the value of the test statistic. Assume that $?A^2=4.8$ and $?{?}^2=6,4$. (Negative value should be indicated by a minus sign. Round final answer to 2 decimal places.)