Introductory Econometrics 4th Edition by Jeffrey Wooldridge

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The variable rdintens is expenditures on research and development (R D) as a percentage of sales. Sales are measured in millions of dollars. The variable profmarg is profits as a percentage of sales.
Using the data in RDCHEM.RAW for 32 firms in the chemical industry, the following equation is estimated:
(i) Interpret the coefficient on log(sales). In particular, if sales increases by 10%, what is the estimated percentage point change in rdintens Is this an economically large effect
(ii) Test the hypothesis that R D intensity does not change with sales against the alternative that it does increase with sales. Do the test at the 5% and 10% levels.
(iii) Interpret the coefficient on profmarg. Is it economically large
(iv) Does profmarg have a statistically significant effect on rdintens