There's a fun interactive datagraphic on gallup.com's website. It's called "State of the States." You can select a polling variable, such as "overall well-being," "support for Obama," or "religiosity," and it will show you how each U.S. state scores on that variable.
Feel free to take a minute to play with the interactive right now. (I'll wait.)
I've pasted a screen shot from the "well-being" results below. Take a look at it, and consider the questions that follow.
a) In the figure above, the variable I selected was "Well being." The thermometer below indicates that darker states are higher in well-being than lighter states. Using that rule, which states are the highest in well-being? Which are the lowest?
b) You might notice that South Dakota is higher in well-being than North Dakota–their shades of green are noticeably different. In fact, you might even imagine a news story in which a reporter suggests that South Dakotans are "happier." But I want you to consider the effect size of the difference. About how much happier are South Dakotans, according to the scale?
Now consider the next screen map (below). This one shows religiosity, indicating the percentage of state residents who consider themselves "Very religious":
c) As before, the thermometer below indicates that darker states are higher in saying they are "very religious" compared to lighter states. Using that rule, what states are the highest in religiosity? Which are the lowest?
d) Take a look at the scale for this variable–what do you notice about the range for Religiosity compared to the range for well-being?
e) On the map, the states of Utah and Idaho are about the same shades of green as South and North Dakota were on the well-being variable. Indeed, the shades of green for Utah and Idaho are noticeably different. In fact, you might now imagine a news story in which a reporter suggests that Utahans are "more religious." Once again, I want you to consider the effect size of the difference. How much more religious are Utahans, according to the scale?
e) What do you think? How is Gallup using these shades of green in this interactive data map? Is their use misleading? If so, what might be better?