# Decision making with two factors

• Apr 20th 2010, 04:24 AM
stefanhendriks
Decision making with two factors
Hi,

Let me state that I am not a math guru, although I love logic, thats why I come here. Perhaps someone can (wants) lend me a hand in approaching this problem.

I try to explain the situation as thoroughly as possible, if you miss any information please let me know.

I am busy with a quality analysis of a software product. I've worked on it quite a bit and it is now boiling down to the question "what is the most interesting part of the software to work on to get the most quality increase with the least amount of effort required".

The total quality of a product is basically the sum of all its properties and how each properties scores. All properties have a relation, meaning one property is more important than another property. Properties in this case are very humanly approaches of quality. Bear with me ok?

What it boils down to is that for each property I now have two variables:
- percentage of how much a property *could* improve
- percentage of how much influence the property has on the currently total score.

To get more concrete, lets say there is property Z:
- it could improve for about 41,90% (you could say, it has now scored 58,10% of its potential)
- it has currently an influence of 8,33% of the total score

I have five other properties with each the same (types of) percentages. (of course, they have different values)

Now i have to make a decision, what property should be worked on? Is it possible to use these two percentages together?

Like I said I am not a math guru, so I simply tried multiplying both percentages.
In this case Z would be : 3,49% (0,4190 * 0,0833). But I don't know its meaning.

Could anyone give me any advice?
• Apr 20th 2010, 01:02 PM
undefined
Quote:

Originally Posted by stefanhendriks
Hi,

Let me state that I am not a math guru, although I love logic, thats why I come here. Perhaps someone can (wants) lend me a hand in approaching this problem.

I try to explain the situation as thoroughly as possible, if you miss any information please let me know.

I am busy with a quality analysis of a software product. I've worked on it quite a bit and it is now boiling down to the question "what is the most interesting part of the software to work on to get the most quality increase with the least amount of effort required".

The total quality of a product is basically the sum of all its properties and how each properties scores. All properties have a relation, meaning one property is more important than another property. Properties in this case are very humanly approaches of quality. Bear with me ok?

What it boils down to is that for each property I now have two variables:
- percentage of how much a property *could* improve
- percentage of how much influence the property has on the currently total score.

To get more concrete, lets say there is property Z:
- it could improve for about 41,90% (you could say, it has now scored 58,10% of its potential)
- it has currently an influence of 8,33% of the total score

I have five other properties with each the same (types of) percentages. (of course, they have different values)

Now i have to make a decision, what property should be worked on? Is it possible to use these two percentages together?

Like I said I am not a math guru, so I simply tried multiplying both percentages.
In this case Z would be : 3,49% (0,4190 * 0,0833). But I don't know its meaning.

Could anyone give me any advice?

Have you taken into account an additional variable representing the "law of diminishing returns"? Basically, the idea is that, the closer you get to perfecting things, the more effort it takes to make small improvements. Since your problem seems more practical rather than theoretical compared with the many other posts in the forum, this might make your model more realistic.

As to your question, it seems like you could think in terms of quality standards, or something along those lines. What I mean is, suppose variable X has percentages (20, 5) respectively according to how you listed them, and Y = (90, 40). Now, if we considered 1 percentage point of improvement the same no matter what, we would have to devote time to Y simply because it has the higher weight. What I mean is, implicitly you are considering that a difference from 20% to 21% is more important than a difference from 90% to 91%, because 20% represents a failure in meeting quality standards.

As to how to change the model to reflect such ideas, I'm not sure, but anyway I think it's an interesting application.

But if I had to follow your model exactly as presented, my guess would be to devote time to the property that has highest weight always, until it reaches 100%, then move on to the one with next-highest weight, etc.