Professor newberg decided to study the social activity level of senior citizens, so he visited a local retirement village and invited residents to participate in a lengthy survey. professor newberg's survey results are probably invalid because he did not use:

A random selection of participants.

In order for professor Newberg's survey to be considered valid, he should have had a random selection of participants, instead.  By doing so, all members would have an equal chance of being included in the study.

this is an outline for the decisions that frankie is going to make

opportunity cost

willingness to buy

price or quality

of course, there could be many economic strategies that should be considered important while making decision. opportunity cost is the foremost significant factor while considering any economic option. when you buy something, you should know how much you are forgoing for this product. indeed, you could buy something different with this measure if you changed your mind. willingness to buy shows how much surplus you are earning while making a decision. it is important because it shows you buy what you want or you buy because you have only limited amount of money. the price or quality can be considered as a general economic option that we are applying while buying something. when you buy something, price or quality could be one of the options. indeed, they define the characteristics of the product.    

mark brainliest!

earlier philosophers whose work influenced the enlightenment included bacon, descartes, locke, and spinoza. the major figures of the enlightenment included beccaria, diderot, hume, kant, montesquieu, rousseau, adam smith, and voltaire. it spread the ideas of the enlightenment across europe and beyond.