Where Do Data Come From?


Where Do Data Come From?


Sacramento Bee/Contributor/Getty Images

CASE STUDY You can read the newspaper and watch TV news for months without seeing an algebraic formula. No wonder algebra seems unconnected to life. You can’t go a day, however, without meeting data and statistical studies. You hear that last month’s unemployment rate was 5.4%. A news article says that 88% of AAAS (the American Association for the Advancement of Science) scientists agree that it is generally safe to eat genetically modified foods, while only 37% of all U.S. residents 18 years of age and over agree. A longer article says that low-income children who received high-quality day care did better on academic tests given years later and were more likely to go to college and hold good jobs than other similar children.

Where do these data come from? Why can we trust them? Or maybe we can’t trust them. Good data are the fruit of intelligent human effort. Bad data result from laziness or lack of understanding, or even the desire to mislead others. “Where do the data come from?” is the first question you should ask when someone throws a number at you.

In 2012, Colorado voters legalized marijuana. Subsequently, voters in several other states have considered legalizing marijuana. One of these is Michigan. In February 2014, the Michigan online news site MLive ran the story “Take our online poll: Should Michigan legalize marijuana?” Of 9684 respondents, 7906 (81.84%) said Yes, 1190 (12.29%) said No, and 588 (6.07%) said Decriminalize but not legalize. These results would seem to indicate overwhelming support for legalizing marijuana in Michigan.

What can we say about data from this poll? By the end of this chapter you will have learned some basic questions to ask about the data from the MLive online poll. The answers to these questions will help us assess whether the data from the poll are good or bad, as we will explore further in Chapter 2.