You are probably well aware that controlled experiments are carried out in laboratories where one sample, say of microbes, is given a treatment and another is given no treatment (the control) and the results are compared. The idea is to hold constant all influences other than the one you wish to test. The same approach is used in controlled agricultural and medical research. But in everyday life it is impossible to carry out experiments on real people and so you have to observe what is happening and then try to control for all other factors; for example, you might try to estimate the effect of a 10% increase in the price of a brand of toothpaste on sales, but a multitude of things can change during the period, such as income, introduction of other brands, new evidence that additives affect decay and so on. Or is it impossible? An intriguing book called The Why Axis by Uri Gneezy and John List (subtitled Hidden Motives and the Undiscovered Economics of Modern Life) published by Public Affairs 2013 shows that randomised field experiments can be carried out and produce really surprising results. Here are just two chapter names:
What can a Matrilineal Society Teach us about Women and Competition?
What seven words can end Modern Discrimination? I don’t hate you, I just like money.
If you want your assumptions about life challenged and get an insight into how you can find things out then I cannot recommend this book highly enough. If, on the other hand, you prefer to live life in a cloud of ignorance then avoid this book.