http://www.joannejacobs.com/2009/02/for-profit-schools-gain-in-philly/ Thinking and Linking by Joanne Jacobs Fri, 10 Feb 2012 04:51:22 +0000 hourly 1 http://www.joannejacobs.com/2009/02/for-profit-schools-gain-in-philly/#comment-43907 Andromeda Thu, 12 Feb 2009 00:50:47 +0000 http://joannejacobs.com/?p=7567#comment-43907 This feels wrong. 25% of a standard deviation is 60% of a year's worth of learning? Shall I conclude that one standard deviation is 2.4 years' worth of learning per year, and conclude thereby that a substantial fraction of students are forgetting more than a year's worth of material per year? I mean, I have a cynical side that is more than happy to cackle over this prospect, and my statistical background is weak, but my husband's isn't and he finds these numbers odd too. Is the thing we're dealing with here not a normal distribution, in which case "standard deviation" is a misleading term? We are baffled. This feels wrong. 25% of a standard deviation is 60% of a year’s worth of learning? Shall I conclude that one standard deviation is 2.4 years’ worth of learning per year, and conclude thereby that a substantial fraction of students are forgetting more than a year’s worth of material per year? I mean, I have a cynical side that is more than happy to cackle over this prospect, and my statistical background is weak, but my husband’s isn’t and he finds these numbers odd too. Is the thing we’re dealing with here not a normal distribution, in which case “standard deviation” is a misleading term? We are baffled.

]]>