Test the Claim That the Samples Come from Populations with the Same

Essay

Test the claim that the samples come from populations with the same mean. Assume that the populations are normally distributed with the same variance.
-At the 0.025 significance level, test the claim that the four brands have the same mean if the following sample results have been obtained. $\begin{array}{llll}\text { brandA }&\text {brand B }&\text {brand C }&\text {brand D }\\\hline15 & 20 & 21 & 15 \\25 & 17 & 22 & 15 \\21 & 22 & 20 & 14 \\23 & 23 & 19 & 23 \\22 & & 18 & 22 \\20 & & & 28\\&&&28\end{array}$