Using a list of “sleep-deprived professions to illustrate statistical and substantive significance”

I ran into a list of “sleep-deprived jobs” yesterday and I think it is a useful tool for illustrating what significance means. The top five sleep deprived jobs (starting with the least rested): home health aide (6 hours, 57 minutes), lawyer, police officers, physicians/paramedics, and economists. The top five jobs with the most sleep (starting with the most rested): forest/logging workers (7 hours, 22 minutes), hairstylists, sales representatives, bartenders, and construction workers. Here is where the data from the list came from:

The lists are based on interviews with 27,157 adults as part of the annual National Health Interview Survey, conducted by a division of the Centers for Disease Control and Prevention. Sleepy’s says its rankings were based on two variables: 1) average hours of sleep that respondents said they got in a 24-hour period, and 2) respondents’ occupations, as they would be classified by the Department of Labor.

Let’s talk about significance. First, statistical significance. The lower value is 6 hours and 57 minutes and the highest value is 7 hours, 22 minutes. We would need to know how the data is clustered, meaning does it look like a normal distribution (meaning most jobs are clumped in the middle) or it is a broader distribution? With a standard deviation, we could figure out how far these highest and lowest values are from the mean and whether they are outside 95% of all the cases.

Perhaps more interesting in this case is the second aspect of significance: even if a case is significantly different from the other cases, is this a meaningful difference in the real world? Just looking at the ten occupations at the top and bottom of this list, the top and bottom are separated by 35 minutes. Would roughly a half hour of sleep really change the quality of life or health between home health aides and forest/logging workers? Of course, sleep might not be the only factor that matters here but is this a meaningful difference? The Mayo Clinic recommends 7-9 hours a night for adults, the National Sleep Foundation also says 7-9 hours a night, and both agree that there are a lot of other factors involved. On the whole then, it appears that the average American (who is in an occupation) is on the low end of recommended sleep (a recurring theme in news stories over the years).

It appears that this list isn’t that helpful if everyone is relatively clustered together. But if we had a little more information, we could know more and determine whether there are (statistically and substantively) significant occupations.

Reaction to Newsweek’s list of “dying cities”

Search for “dying city” and “Newsweek” and what you will see in the Google results is not the original article but rather reactions from some of the listed cities. Newspapers in South Bend, Rochester (NY), and Grand Rapids have voiced their displeasure.

This recent list from Newsweek is based on Census data and the cities that experienced the greatest population declines from 2000 to 2009:

We used the most recent data from the Census Bureau on every metropolitan area with a population exceeding 100,000 to find the 30 cities that suffered the steepest population decline between 2000 and 2009. Then, in an attempt to look ahead toward the future of these regions, we analyzed demographic changes to find which ones experienced the biggest drop in the number of residents under 18. In this way, we can see which cities may have an even greater population decline ahead due to a shrinking population of young people.

Here are the 10 cities that had the steepest drop in overall population as well as the largest decline in the number of residents under the age of 18.

Some thoughts about this data:

1. All of these cities, except two (one in FL, one in CA), are in the Rust Belt. Many of these cities are not surprises.

2. The local reactions seem to be expressions of civic pride. People in these cities can’t ignore the population loss but they are right in saying their cities are not going completely to waste. There are some good things going on in these places but broader population trends are working against them.

3. “Dying city” does not equal “dead city.” Dying doesn’t mean that everybody is leaving, just that these cities lead the country in percentage population loss. A real “dead city” would have no population left. These cities are from that point.

4. Perhaps what angers locals most is that articles like these can further negative stereotypes. These places already suffer from perception problems and lists like this do not help. For example, it is any surprise that Detroit continues to lose population after years of commentators saying how bad of shape Detroit is in? People probably leave places like Detroit for reasons more important than punditry (reasons like jobs, opportunities, etc.) but it could play some role.