Statistics Problems from Physical Chemistry

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Homework Help Overview

The discussion revolves around a statistics problem related to trace elemental zinc content in a high purity gold sample. Participants are tasked with calculating the zinc content and its uncertainty at a 95% confidence limit based on provided data values.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss calculating the average and converting measurements, while questioning the method for determining uncertainty at a 95% confidence level. There is also a consideration of whether the multiplication by kg of Au is necessary for the analysis.

Discussion Status

The conversation is ongoing, with some participants seeking clarification on the appropriateness of their calculations and the relevance of certain steps to the original question about confidence intervals. There is no explicit consensus yet on the best approach to take.

Contextual Notes

Participants note potential challenges with the material, suggesting that it may not be straightforward and could be perceived as "unfair" if not adequately covered in their resources.

Ki-nana18
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Homework Statement


The following data were obtained for trace elemental zinc in a particular sample of high purity (%Au> 99.99%). The results are given in mg Zn/ kg Au.

15.38, 15.17, 15.33, 14.88, 14.71, 15.42, 15.60, 15.22

Find the zinc content and the uncertainty at 95% confidence limit.

Homework Equations



Molecular weight of gold: 196.966569 g mol-1

The Attempt at a Solution


I found the average of all the values, then converted to mg of Zinc by multiplying the kg of Au. I'm not really sure on how to find the uncertainty at 95% confidence.
 
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Ki-nana18 said:

Homework Statement


The following data were obtained for trace elemental zinc in a particular sample of high purity (%Au> 99.99%). The results are given in mg Zn/ kg Au.

15.38, 15.17, 15.33, 14.88, 14.71, 15.42, 15.60, 15.22

Find the zinc content and the uncertainty at 95% confidence limit.

Homework Equations



Molecular weight of gold: 196.966569 g mol-1

The Attempt at a Solution


I found the average of all the values, then converted to mg of Zinc by multiplying the kg of Au. I'm not really sure on how to find the uncertainty at 95% confidence.

Find the sample mean and sample standard deviation of your data above, then use the t-distribution to determine a confidence interval.

If you have never seen this type of material before, or if your textbook or notes have not done it, the assignment question could be counted as "unfair": this type of material is not always easy to grasp, and it takes practice to understand it. On the other hand, if it is in your book or notes, why don't you just follow the method therein?

RGV
 
So multiplying by kg of Au was right?
 
Ki-nana18 said:
So multiplying by kg of Au was right?

It depends on what you want to measure. You could just take the original measurements, without any multiplication, and that would give you inferences about mg of Z per kg Au. If you want something else, do the conversion.

However, this has nothing at all to do with the question you were asked, which was about confidence intervals.

RGV