The Elsmar Cove Business Systems and Standards Discussion Forums Statistical Comparison of Product: High Average vs. Low Range
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# Statistical Comparison of Product: High Average vs. Low Range - Page 2

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Post Number #9
7th February 2013, 06:36 PM
 Miner Total Posts: 4,336
Re: Statistical Comparison of Product: High Average vs. Low Range

First, be sure that your data is normally distributed. While not unheard of, it is unusual for reliability data to be normally distributed. Then I would determine and compare the B10 lives of the products. B10 is the tenth percentile, or the time at which 10% of the product could be expected to have failed.

Post Number #10
7th February 2013, 11:31 PM
 reynald Total Posts: 283
Re: Statistical Comparison of Product: High Average vs. Low Range

Quote:
 In Reply to Parent Post by FPT2001 How do I evaluate benefits of a higher Mean compared to other products that have a much tighter range and/or Stddev?
Are you talking about the mean/std dev of the resistance here? i have the impression that this can be done by showing the histogram of the resistances and adding the specifications as a reference. Then compute the process capability. By then you could objectively assess which one is better, the higher mean or the tighter range. I guess that should do it unless i totally mis-interpreted the question.
Regards,
Reynald
 Thanks to reynald for your informative Post and/or Attachment!
Post Number #11
7th February 2013, 11:58 PM
 FPT2001 Total Posts: 12
Re: Statistical Comparison of Product: High Average vs. Low Range

There is no specification, only a testing procedure. This is why this is more difficult to quantify. We want a method to compare results and assume the higher number is a better product.

Given the data supplied, assume a higher value is a better product, is the product with a high avg/high range better than the product with a lower avererage/lower range ?
Post Number #12
8th February 2013, 03:39 PM
 Bev D Total Posts: 3,606
Re: Statistical Comparison of Product: High Average vs. Low Range

Quote:
 In Reply to Parent Post by FPT2001 Given the data supplied, assume a higher value is a better product, is the product with a high avg/high range better than the product with a lower avererage/lower range ?
Well, I would start with a simple plot of the data. The individual data points for each product. This will tell you more about what is going on then any statistical analysis. By looking at the data you can pick out what aspects you want your marketing folks to concentrate on and even determine which statistic will be helpful.

I put together a really quick set of plots showing the differences between the products using the summary statistics you provided. It is attached.

Of course which is better is really a function of the use. as you know, some customers may value predictable life even if the life is shorter. That said the longer product appears (since I don't know the shape of the distribution) to be substantially longer life...
Attached Files: 1. Scan for viruses before opening, 2. Please report any 'bad' files by Reporting this post, 3. Use at your Own Risk.
 Spring Data.xls (18.0 KB, 47 views)
Post Number #13
14th February 2013, 10:27 AM
 Darius Total Posts: 553
Re: Statistical Comparison of Product: High Average vs. Low Range

Quote:
 In Reply to Parent Post by FPT2001 There is no specification, only a testing procedure. This is why this is more difficult to quantify. We want a method to compare results and assume the higher number is a better product. Given the data supplied, assume a higher value is a better product, is the product with a high avg/high range better than the product with a lower avererage/lower range ?
Put your self in the place of your customer, if you could buy a light bulb and have 2 options:
1- it could last 1 year but you could not be sure if it could last 10 or 14 months
2- a ones that last exactly 5 months (no less or more days)

Wich one does you buy?, But if you do parts for planes, wich one does you buy (you can tell your costumer to replace the parts as a periodical maintennance routine)?
Post Number #14
14th February 2013, 01:44 PM
 BethP Total Posts: 48
Re: Statistical Comparison of Product: High Average vs. Low Range

At the company I work, we make a number of product claims against competitor products. These are made VERY carefully with guidance from our in house legal team because the competitor products have a tendency to fight anything that is printed on packaging or advertised. From a testing perspective, we try to work with ASTM and other standard test protocols as much as possible with independent test labs performing the tests. Additionally, we test enough samples to determine whether we have a normal distribution and can statistically show that we are better, stronger, faster, etc. The challenge is that the marketing team is not always patient with the technical team.

I echo the advice already written - think about the product from the consumer perspective - what are the significant factors in their buying decisions? what comparisons do they make to determine who to purchase from? It could be that favorable credit terms are a more important deciding factor than product lifespan.

Last edited by BethP; 14th February 2013 at 01:46 PM. Reason: fix wording

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