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Narrative about change in standard deviation

  • 27-04-2012 2:04pm
    #1
    yellow hen
    Registered Users, Registered Users 2 Posts: 4,041 ✭✭✭


    I want to write an observaation about a change in standard deviations between two dates. Eg. When talking about the range of bodyfat observed for candidates on a weightloss programme, in 2009 the standard deviation was 8.75 and in 2012 it was 19.81. How exactly do i construct a sentence to say this?
    thanks.


Comments

  • #2
    Ostrom
    Registered Users, Registered Users 2 Posts: 3,483 ✭✭✭Ostrom


    Exactly as you have here I'd say, depending on the context of the sentence. What were you concerned about?


  • #3
    yellow hen
    Registered Users, Registered Users 2 Posts: 4,041 ✭✭✭yellow hen


    Can you say that the standard deviation increased over 100% from 8.75 to 19.81?


  • #4
    hivizman
    Registered Users, Registered Users 2 Posts: 1,163 ✭✭✭hivizman


    Are the two groups (2009 and 2012) the same people, or different people? Are the measurements before or after the weight loss treatment? What is the mean weight of the group in 2009 and in 2012? If the means are roughly the same in 2009 and 2012, you could say that the weights are more widely dispersed in 2012 than in 2009. But is this before or after the treatment?

    You can use the F-test to investigate whether the difference between the two standard deviations (or strictly the variances) is statistically significant.


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