A researcher decides to investigate whether there are any changes in people's IQ scores from early adulthood through middle adulthood. He begins with a sample of 21-year-olds and plans to follow this group until they are 50 years old. The type of research design he is planning to use is called

This is called an "OBSERVATIONAL RESEARCH".

Explanation: An Observational research is a type of research were we get our result by observing samples act on it own natural course, without influencing it with any substance. We have two type of research design, Experimental and Observational research design.

Because the researcher has chooses a particular group and decide to observe them, grow and act on their natural course, without giving any substance to them, his research model is Observational.

Experimental research design is when a substance is added to a sample to compare it with another sample

for many centuries there were important factors which the economies of the muslim empires developed increasingly. they applied economic procedures in production, investment, finance, taxation and property. they used to tax certain goods (for example: harvest), they charged interest on money lent, they signed contracts with merchants; they relied on a common currency, and they used checks as well as promissory notes. with the money collected by means of taxation, the government provided the needy with an income. in addition, trading networks covered huge distances, so far regions started to have contact and exchange goods. this trade network covered areas of asia, africa and europe.

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