Fire/Arson Investigations : Fire/Arson Investigations
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Re: Significant error rate
Posted by: Jim Mazerat (IP Logged)
Date: February 14, 2007 10:50AM
Steve:
We are in total agreement. I think there are a lot of investigators out there have the problem understanding the idea of having confidence in the belief and that confidence being different from the confidence that they have discovered the actual cause. When I talk with others about this topic you can see the confusion in their face. Then I wonder if I am confusing other investigators how confusing would this be to the trier of fact, and would it just muddy the water around the fact so the facts are indiscernible. I understand much of this is theoretical and will never make it to the court room, but what if it does.
When it comes to labeling for the purpose of explanation I wonder if you get to a point in an explanation to where you do more to confuse the issue rather than clarify. I wonder if in the instruction you would explain the point that you want the investigator to do what is necessary to where he or she believes they have reached the correct conclusion, and not put specific labels to indicate the level of confidence, would that not be a better method of teaching. I want that investigator to be confident in the determination reached and be satisfied they have examined all available data to reach that conclusion. To me it is as simple as you know the cause or you do not. If there is any question remaining then it is undetermined until that question can be addressed.
You hit the nail on the head when you said, “It seems that any attempt to label an absolute level of certainty becomes an infinitely regressing argument that is ultimately inconclusive.”
This is where we totally agree, in that putting a label or word on your level of confidence does not make it right. I was at a trial where a jury did their own investigation based on photographs being used during the trial. Both experts agreed as to the room of origin but the jury put the fire in a different room. I believed this occurred because the testimony of the experts was more aimed at destroying the others opinion than it was supporting their own. Some of the labels we have talked about were used in that case by the different experts.
I guess what this posting was about was not so much the subject but the perception another person may develop based on the labels being used and their definitions. Most people on the jury will not understand the difference between your confidence in the belief and that confidence being different from the confidence you have in the discovery of the actual cause. If the person you are communicating with does not understand the information, it is natural that this person will fill what is not understood with information that has been learned in the past. Now where are we? A person could take the definition of “Probable” as it is listed in 921 an make the assumption that if you only have a level of confidence of 51% that you opinion is correct that it is logical that there is a 49% chance you opinion is wrong. Where this would not be what the expert is attempting to convey it very well could be the end result. How would this idea affect the weight they give to his opinion?
If there was a high school biology teacher on the jury, and this person hears the percentages being used by the experts as to there level of confidence as to their opinion there may be a problem. I went to a local high school a spoke with the teacher mentioned above. I read the definition of “Probable” out of 921 to her. The first thing she said was this topic has nothing to do with science. When asked why, she said that in science they have what is called the significant error rate and that this error rate is normally no greater than 5%. She said she uses a Time Life video program in her instruction to her class that has this information. Now I not only have a teacher that if on the jury would have a problem with our terminology and definitions but also any other person that has seen these instructional tape. If I fail to know that a difference exist, and fail to explain this difference adequately then there is a possibility one of these persons if on the jury would be telling the others I had a 49% error possibility.
When we develop wording for classes or documents we need to understand who may become the audience.
Jim
We are in total agreement. I think there are a lot of investigators out there have the problem understanding the idea of having confidence in the belief and that confidence being different from the confidence that they have discovered the actual cause. When I talk with others about this topic you can see the confusion in their face. Then I wonder if I am confusing other investigators how confusing would this be to the trier of fact, and would it just muddy the water around the fact so the facts are indiscernible. I understand much of this is theoretical and will never make it to the court room, but what if it does.
When it comes to labeling for the purpose of explanation I wonder if you get to a point in an explanation to where you do more to confuse the issue rather than clarify. I wonder if in the instruction you would explain the point that you want the investigator to do what is necessary to where he or she believes they have reached the correct conclusion, and not put specific labels to indicate the level of confidence, would that not be a better method of teaching. I want that investigator to be confident in the determination reached and be satisfied they have examined all available data to reach that conclusion. To me it is as simple as you know the cause or you do not. If there is any question remaining then it is undetermined until that question can be addressed.
You hit the nail on the head when you said, “It seems that any attempt to label an absolute level of certainty becomes an infinitely regressing argument that is ultimately inconclusive.”
This is where we totally agree, in that putting a label or word on your level of confidence does not make it right. I was at a trial where a jury did their own investigation based on photographs being used during the trial. Both experts agreed as to the room of origin but the jury put the fire in a different room. I believed this occurred because the testimony of the experts was more aimed at destroying the others opinion than it was supporting their own. Some of the labels we have talked about were used in that case by the different experts.
I guess what this posting was about was not so much the subject but the perception another person may develop based on the labels being used and their definitions. Most people on the jury will not understand the difference between your confidence in the belief and that confidence being different from the confidence you have in the discovery of the actual cause. If the person you are communicating with does not understand the information, it is natural that this person will fill what is not understood with information that has been learned in the past. Now where are we? A person could take the definition of “Probable” as it is listed in 921 an make the assumption that if you only have a level of confidence of 51% that you opinion is correct that it is logical that there is a 49% chance you opinion is wrong. Where this would not be what the expert is attempting to convey it very well could be the end result. How would this idea affect the weight they give to his opinion?
If there was a high school biology teacher on the jury, and this person hears the percentages being used by the experts as to there level of confidence as to their opinion there may be a problem. I went to a local high school a spoke with the teacher mentioned above. I read the definition of “Probable” out of 921 to her. The first thing she said was this topic has nothing to do with science. When asked why, she said that in science they have what is called the significant error rate and that this error rate is normally no greater than 5%. She said she uses a Time Life video program in her instruction to her class that has this information. Now I not only have a teacher that if on the jury would have a problem with our terminology and definitions but also any other person that has seen these instructional tape. If I fail to know that a difference exist, and fail to explain this difference adequately then there is a possibility one of these persons if on the jury would be telling the others I had a 49% error possibility.
When we develop wording for classes or documents we need to understand who may become the audience.
Jim
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