Introduction to Understanding Trends
"How Are We Doing?" Understanding Trends • 5m 37s
What explains a trend we see in the numbers? There are five explanations for numbers that show change over time and it's important to be aware of them so we don't make strategic mistakes: (1) real change, (2) changes in the population size, (3) changes in the definition of the thing we're tracking, (4) changes in the environment or in related behaviors that affect the numbers, and (5) changes in how we gather data. All of these things can happen at once, and they all can affect the data to varying degrees.
Up Next in "How Are We Doing?" Understanding Trends
Changes in Size: Using Rates vs. Totals
When we explore trends, it's easy to mistake a change in population size for a change in something else. This is why rates are useful. Rates tell us how something is changing per unit or member of the population, which lets us control for changes in the population.
Change in Definition
Lots of the things that interest us have definitions that are not stable over time, especially in areas involving human behavior. When these definitions change, it can affect data on those things. Does this mean definitions should never change? No. But when they do, we should be aware of those ch...
Changes in Behavior/Environment
There is a difference between what is happening in the environment and what we observe in our data. Sometimes, the environment (or a behavior in it) changes in ways that affect our data and create a mistaken impression of change in the thing that really interests us. When you see a big change, co...