As their names imply real GDP is better used than nominal GDP. Nominal GDP is the raw or crude GDP whereas real GDP is the more standardized.

If the study deals with more than one country, I think GDP in purchasing power parity; "GDP-PPA" is more adequate than GDP at constant or real price

Thank you all for your very knowledgeable answers. It is good that blind guides should stop leading in fashioning out models for our research students. When supervisors are not well tutored in certain areas of specialization they should rather keep mute rather than argue in something they have little knowledge of. Young and middle level academics who are still under the tutlege of seniors should stop portraying attitude of masters when they are still growing in knowledge and stop parading themselves as have ''arriveds'' when in fact they still have a lot to learn from established professors or senior academics in individual areas of specialization. A word is enough fro the wise.

I have in all humility discovered through experience over the years in the management sciences and economics that people of late people rarely become experts in a field of specialization when they do not hold a first degree in that area. What happens is that people forcefully switch over from One functional area like accounting or economics into finance to do MBA and PhD or MSc and PhD without BSc in banking /finance and some did not even do PGD and switch over to finance and with open eye contesting authority in banking and finance after making a few publications from mostly students projects and in a worse scenario from plagiarized textbooks and papers written by others. In my region in SSA this practice has virtually destroyed the fabrics of academic quality in our dispensation. Thank you as we try to modify and improve in our supervision and research paper writing.