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Old 11-04-2009, 09:36 PM   #11 (permalink)
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Originally Posted by Drum View Post
I read all that, and I tried to understand, but you use too much jargon that explains little about what you are proposing and, more importantly, how it is different or better.

I realize that you guys haven't done any actual testing yet, but it might help me to understand this better if you could give an example of how you would express the results of a theoretical test like you propose.

Thanks in advance,
D

[PS: I don't understand all of what Harb or really, anyone from Fubarius' post down has written, so you must consider me a pretty uninformed audience.)
we plan to use an identical method to all of our accuracy tests. our data consists of a table with initial velocity, X impact, and Y impact. if the chrono speed is to high or low, we can filter that out (even with consistent guns you can get all manner of weird spikes, more then likely bad paint). the from the X and Y impacts, we find out the statistical distribution by computing the standard deviation. from this standard deviation we produce a distribution map in the form of a normal curve that we express as a single number - the vector.

now, using the standard deviation and basic Z table, we can compute any radius based on any level you please. one standard deviation happens to be about 68% confidence, however, if you wanted you could choose a 90%, or a 20% confidence level. basically all that means is a different radius which represents a circle which will have whatever percent your specified level is will fall into it.

we happen to express it as one vector simply out of convenience, and because 68% is a pretty representative and realistic number to look at for accuracy. the calculations to get any different percent (or to calculate a percent based on a given radius) are fairly trivial.
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Old 11-04-2009, 09:42 PM   #12 (permalink)
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Alas, so often your answers only raise more questions in my ill trained mind.

Just for starters, I am not understanding what "x and y" shots are supposed to represent. Think of me as a little kid you were trying to educate, please.

I would reiterate my request for an example of what your data would look like. In graph form? Or written out, maybe? You see, I am not even sure what it would look like.

Thanks again,
D

Edit: Also, I am not aware of the meaning of the word "confidence" as used in your explanation above. Another example of my cluelessness.
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Old 11-04-2009, 09:48 PM   #13 (permalink)
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... frankly, i think its a bad thing that poeple don't want to learn why and how we analyze our data. if poeple don't know why or how, then the ideal is to teach them, not dumb it down for them. then next time around they have the skills they need to look at a statistical sample and understand it. education is part of the overall plan...
Here is one of the big issues in all of these discussions. If you want to teach people, you need to be able to explain when the questions are asked. On average, this is not be accomplished. "Dumbing it down" is necessary for those to learn and understand. Once they understand, then the proper term will be understood and points will be made clear.

For example, if I just posted the following, very few will actually know what it is:

The new address lengths support more levels of addressing hierarchy, a much greater number of addressable nodes, and simpler auto-configuration of addresses.
Addresses beginning with 80 zeros are reserved for IPv4. Separate prefixes for provider-based and geographic-based addresses. The geographic-based structure is divided up in much the same fashion as the current Internet. The last 15 bits of the provider-based addresses can be divided up at the provider's discretion. Flags within the multicast addresses differentiate between permanent and transient groups and now has a scope field to allow the multicast to be limited to a particular link, site, organisation, etc.
The notation for writing IPv6 addresses is to write it them as 8 groups of four hexadecimal digits with colons between the groups.
8000:1234:0345:4321:1234:0000:0000:abcd


To explain IPV6, I would have to dumb it down so people will understand, then build it back up.

so, if education is part of the plan, pay attention to your professors. You had no idea what vortex shedding was a year or so ago. They started dumb and built it up

oh, finally, people want to learn. With the majority of posts, it feels like you talk down to people. This is a personal observation. Remember when you didn't know your trade. I don't like people who talk down to me and I will refuse to learn what you have to say.
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Old 11-04-2009, 09:58 PM   #14 (permalink)
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The problem though, is that you'll have to define the following terms...

Standard Deviation.
Distribution Map
Normal Curve
Vector (I recommend re-naming this one to "Distance from pattern center")
Confidence Level

These are not terms used in common every day language, or really anything out side of a statistics class. And just in case, I'd use "average" every time you're tempted to use the word "mean". While mean may mean what it means its mean to use mean when there's another word with similar meaning, since mean can mean a lot more than you meant it to mean. You see what I mean?

I run into something similar at work. I run a CNC router, and to any machinist "Speed" refers to bit RPM, and "Feed" refers to the rate of bit (or part) travel. But when my boss comes up to me and wants to talk about increasing "Speed", I know he's NOT talking about RPM.

And a quick clarification, do you use the standard deviation for the complete population, or are you using it for a sample population?
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Old 11-04-2009, 10:01 PM   #15 (permalink)
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Drum, x and y values are impact locations on our target in inches.

tpx stiffi accuracy

here's an example of our data sheets. I like graphs too - like the ones on this sheet:

Barrel vs Accuracy Test

Confidence is a way to tell people how good your data is. basically it's a way to test to see how qualified your data is. We normally use it to see if we can state something about performance.

So, for example, let's say that we shot four barrels - there was some difference in vector - but not very much. We might check the confidence interval and find out that our test wasn't large enough to actually say that one was better than another.
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Old 11-04-2009, 10:04 PM   #16 (permalink)
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Originally Posted by Drum View Post
Alas, so often your answers only raise more questions in my ill trained mind.

Just for starters, I am not understanding what "x and y" shots are supposed to represent. Think of me as a little kid you were trying to educate, please.

I would reiterate my request for an example of what your data would look like. In graph form? Or written out, maybe? You see, I am not even sure what it would look like.

Thanks again,
D
X and Y are a set of axis. one perpendicular to the other. like math class.

each shot gets a triple data point, its X impact (where the ball hits measured against the X axis), its Y impact and a chrono speed.

so heres an example -

YouTube - hammerhead accuracy test

produced this data sheet - HammerHead Test

at teh top of which is some setup info, and each barrel with the shots fired through its information. we most of the time take a tad of 20 shots, so that we can filter the results a bit by chrono speed.

underneath the data is some computations based on that data, we compute the mean mostly because its easy, not because it matters, which is just the center point of all the shots in that sample. the "SD" is the standard deviation, which is a representation of normal distribution for that set of data. then the SD from both the X and Y are combined into a vector which is highlighted in yellow.

now that number is the radius of a circle which should include 68% of all shots fired through that setup (not just the sample, ALL shots fired).

computing a different percent's associated radius, say if you wanted to know 75% or 95% you can compute the radius, of if you have a radius and want to know how many of the shots will fall into it, you can do that too.

however, for comparative purposes, we conveniently use a ciricle with one standard deviation just because it is convent. if the 68% or one standard deviation is the same for two setups, then the normal curves or probability distribution will be the same for those two setups, and we can conclude then are equally accurate.


this differs from carter/gimilsim/x3/tibarms method because the circle (even if you drop a few outliers) is arbitrary and represents nothing in the real world. for that circle that cart quotes we can't examine what probability anything has, and as in TKs example, we can have patterns that have identical ranges (thats the distance from one side to the other), and yet have different accuracies.

an analogy that most poeple should get is this one -

say two classes take identical tests.

in one class there are

5 in the 90s
10 in the 80s
15 in the 70s
10 in the 60s
5 in the 50s

in the other class there are

1 in the 90s
3 in the 80's
38 in the 70's
2 in the 60's
1 in the 50s

which class scored closer to 75% on the test?

you could argue the first one did, because the mean is 75%. you could also argue that the second one did too, because it is also 75% (close enough). then you could look at the range of the data, and both are over a 50% range. so you can't use the range either. this is like carter/x3/gimilsim/tibarms method. with only those tools, its possible to not be able to tell the difference between these two data sets.

so who scored closer to 75% on the test?

while, since we know the distribution of the scores, we can compute the standard deviation, which just figured from my butt is probably about 12-15% for the top one, and probably 7% or so for the bottom one.

so the second class is significantly closer to 75%.
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Old 11-04-2009, 10:07 PM   #17 (permalink)
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Okay Bryce, that was helpful. I am almost there.

Looking at the charts, I am still not clear on what is the difference between x and y.

Take shot #1 on either of those charts. It has both an X and a y. How is a single shot scored twice or... what is going on there?

Thanks,
D

Edit: Sent this before I saw your post, cp, I will read yours now.
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Old 11-04-2009, 10:13 PM   #18 (permalink)
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Okay Bryce, that was helpful. I am almost there.

Looking at the charts, I am still not clear on what is the difference between x and y.

Take shot #1 on either of those charts. It has both an X and a y. How is a single shot scored twice or... what is going on there?

Thanks,
D

Edit: Sent this before I saw your post, cp, I will read yours now.
if you watch the video, the X and Y represent the vertical (Y) and horizontal (X) location on that big white and red board.
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Old 11-04-2009, 10:18 PM   #19 (permalink)
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Quote:
Originally Posted by Drum View Post
Looking at the charts, I am still not clear on what is the difference between x and y.

Take shot #1 on either of those charts. It has both an X and a y. How is a single shot scored twice or... what is going on there?
Think of it as playing a game of Battleship. It's a location on a grid. Can't really be considered a "score", unless the pattern happens to land on the arbitrary center of the grid. But when used as a method of determining location we can do further calculations with it.
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Old 11-04-2009, 10:24 PM   #20 (permalink)
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Originally Posted by Drum View Post
Okay Bryce, that was helpful. I am almost there.

Looking at the charts, I am still not clear on what is the difference between x and y.

Take shot #1 on either of those charts. It has both an X and a y. How is a single shot scored twice or... what is going on there?

Thanks,
D

Edit: Sent this before I saw your post, cp, I will read yours now.
yup,

x is inches left (negative) or right (positive) of the center of the target.

y is inches above (positive) or below (negative) the center of the board.

The calculation for standard deviation already includes the center of the group - so you don't have to actually hit the middle of the board to calculate it. Basically a standard deviation is the average distance of every shot from the average of all the shots. So, it's the average distance from the middle of all the shots to each of the shots.
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