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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Procrastinate on September 01, 2011, 07:46:49 AM

Title: Imprecise Chemistry Titrations
Post by: Procrastinate on September 01, 2011, 07:46:49 AM

I was just wondering, if you did a number of Chemistry titrations and none of the results were in 0.1mL agreement, what would be the best way to solve problems with that imprecise data? If you didn't have time to repeat the experiment, what would be the best way to tackle this problem when you are taking the mean value of them?

Title: Re: Imprecise Chemistry Titrations
Post by: Borek on September 01, 2011, 12:20:51 PM

I am not aware of anything better than average.

Title: Re: Imprecise Chemistry Titrations
Post by: Arkcon on September 01, 2011, 12:54:50 PM

It might be appropriate to include the standard deviation as well as the mean, so you can claim to have given the "best answer" you data allows you to.  It is really up to the instructor if you can exclude an outlier to improve your average or standard deviation, if you have the skill, maybe you can perform an ANOVA to determine if an outlier is too far out depending on your confidence level.  (I've only heard of people doing an ANOVA, I've never done one myself, so fair warning there.)

Title: Re: Imprecise Chemistry Titrations
Post by: Procrastinate on September 02, 2011, 09:23:29 PM

Quote from: Arkcon on September 01, 2011, 12:54:50 PM

It might be appropriate to include the standard deviation as well as the mean, so you can claim to have given the "best answer" you data allows you to.  It is really up to the instructor if you can exclude an outlier to improve your average or standard deviation, if you have the skill, maybe you can perform an ANOVA to determine if an outlier is too far out depending on your confidence level.  (I've only heard of people doing an ANOVA, I've never done one myself, so fair warning there.)

Thanks for that. That is actually quite a good idea. I did my Statistics Unit last Semester and I did learn how to do an ANOVA.

Title: Re: Imprecise Chemistry Titrations
Post by: BluePill on September 03, 2011, 10:38:14 AM

You could use the test for outliers. In memory, I think it can be found in Skoog, et al "Fundamental of Analytical Chemistry".

Title: Re: Imprecise Chemistry Titrations
Post by: 408 on September 03, 2011, 11:00:26 AM

Do you have a 'feel' for the data?  Did some trials you know you perfectly hit the endpoint, where as others you screwed up.  If I do that I weight the ones I feel better about heavier than the ones that I think were not perfect.  Yeah, kinda my improvised sketchy method, but it has never steered me wrong.