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.