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yellow hen · 27-04-2012, 15:04

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.

**efla** · 29-04-2012, 23:35

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

yellow hen · 30-04-2012, 07:29

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

**hivizman** · 30-04-2012, 11:22

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.

27-04-2012, 15:04	#1
yellow hen Registered User Join Date: Oct 2011 Posts: 1,198 Adverts \| Friends	Narrative about change in standard deviation 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.

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29-04-2012, 23:35	#2
efla Moderator Join Date: Jul 2006 Location: Kildare Posts: 3,319 Adverts \| Friends Mod: Anthropology, Sociology & Culture	Exactly as you have here I'd say, depending on the context of the sentence. What were you concerned about?

30-04-2012, 07:29	#3
yellow hen Registered User Join Date: Oct 2011 Posts: 1,198 Adverts \| Friends	Can you say that the standard deviation increased over 100% from 8.75 to 19.81?

30-04-2012, 11:22	#4
hivizman Moderator Join Date: Jun 2007 Location: In exile Posts: 1,157 Adverts \| Friends Mod: Islam	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.