Question $3.$ The GDP from $2015-2017$ for the 'Manufacturing' industry, is provided in the NWPB$/$GDP$.$xlsx Excel file. Compare the contributions to GDP by the Manufacturing industry for the three years.

$($a$)$ Can we infer at the $5\%$ significance level that the average GDP for all years between $2015$ and $2017$ for the Manufacturing industry is different? Should we reject or not reject the claim that there is no difference in the population means? Give an explanation for your conclusion.

$($Hint: Perform the ANOVA test of comparison of the population means. Take the samples: GDPs for Manufacturing from $2015$ to $2017$ from the file NWPB$/$GDP$.$xlsx$.)$