Can anyone tell me what the initials ES an SD represent?
How is it measured?
How is it measured?
Help A newbie please
- Thread starter weedwacker
- Start date
Forum Boss
Administrator
ES = Extreme Spread
SD = Standard Deviation
This can be used in describing velocities, or measurement variable, such as the ES of bullet overall length or the SD of weight variances in brass.
In a velocity calculation the ES would be the Highest recorded speed minus the lowest speed. For example, if a chronograph reports 2900, 2850, 2820, 2870 and 2880, the ES would be 2900 - 2820, or 80 FPS.
Using the same number, the Standard Deviation is the calculated predicted variance from the mean,average) value. You can enter your values in an Excel spreadsheet and it will calculate the SD for any set of numbers. Most chronos will do this as well. It is easier to use these tools rather than do the raw calculation:
Here's what Oehler, the chronograph company, says: "What is standard deviation and what does it mean? Because standard deviation and average go hand-in-hand, let's first talk about averages. If you talk about average velocity, everyone knows what you mean. You measure the velocity of several shots and you average your readings. If someone asks you the velocity of that ammo, you say that it's about 2950 feet per second. You naturally quote the average velocity, and the listener understands. You know that some shots will be faster than average and some will be slower. You don't even worry about the exact definition of average; it's about the middle.
Confusion doesn't come until someone asks if the velocity is uniform. You are comfortable with quoting the average velocity, but you know that it doesn't tell the whole story. The average does not tell you how much the velocity readings scatter above and below the average. How do you describe uniformity or assign it a number grade? The standard deviation is a number that describes uniformity. The smaller the number, the more uniform velocity. A standard deviation of zero means every velocity was the same. A standard deviation of 29 fps means you expect two-thirds of the individual velocities to be within 28 fps of the average."
Reference,quoted below): http://www.gcseguide.co.uk/standard_deviation.htm
The standard deviation measures the spread of the data about the mean value. It is useful in comparing sets of data which may have the same mean but a different range. For example, the mean,average) of the following two sets of numbers is the same: 15, 15, 15, 14, 16 and 2, 7, 14, 22, 30.
However, the second set,2, 7, 14, 22, 30) is clearly more spread out. If a set has a low standard deviation, the values are not spread out too much.
In shooting, particularly when looking at bullet velocities, low SD is the "holy grail". It demonstrates that the load is very consistent. Low ES is also very important, because, at long range, just one round that is very much slower or faster than the rest can ruin a group,or score).
SD = Standard Deviation
This can be used in describing velocities, or measurement variable, such as the ES of bullet overall length or the SD of weight variances in brass.
In a velocity calculation the ES would be the Highest recorded speed minus the lowest speed. For example, if a chronograph reports 2900, 2850, 2820, 2870 and 2880, the ES would be 2900 - 2820, or 80 FPS.
Using the same number, the Standard Deviation is the calculated predicted variance from the mean,average) value. You can enter your values in an Excel spreadsheet and it will calculate the SD for any set of numbers. Most chronos will do this as well. It is easier to use these tools rather than do the raw calculation:
Here's what Oehler, the chronograph company, says: "What is standard deviation and what does it mean? Because standard deviation and average go hand-in-hand, let's first talk about averages. If you talk about average velocity, everyone knows what you mean. You measure the velocity of several shots and you average your readings. If someone asks you the velocity of that ammo, you say that it's about 2950 feet per second. You naturally quote the average velocity, and the listener understands. You know that some shots will be faster than average and some will be slower. You don't even worry about the exact definition of average; it's about the middle.
Confusion doesn't come until someone asks if the velocity is uniform. You are comfortable with quoting the average velocity, but you know that it doesn't tell the whole story. The average does not tell you how much the velocity readings scatter above and below the average. How do you describe uniformity or assign it a number grade? The standard deviation is a number that describes uniformity. The smaller the number, the more uniform velocity. A standard deviation of zero means every velocity was the same. A standard deviation of 29 fps means you expect two-thirds of the individual velocities to be within 28 fps of the average."
Reference,quoted below): http://www.gcseguide.co.uk/standard_deviation.htm
The standard deviation measures the spread of the data about the mean value. It is useful in comparing sets of data which may have the same mean but a different range. For example, the mean,average) of the following two sets of numbers is the same: 15, 15, 15, 14, 16 and 2, 7, 14, 22, 30.
However, the second set,2, 7, 14, 22, 30) is clearly more spread out. If a set has a low standard deviation, the values are not spread out too much.
In shooting, particularly when looking at bullet velocities, low SD is the "holy grail". It demonstrates that the load is very consistent. Low ES is also very important, because, at long range, just one round that is very much slower or faster than the rest can ruin a group,or score).
Fred Bohl
Gold $$ Contributor
Paul's explanation and formula are correct for the standard deviation of a sample from a large set of data that follows the "normal" or Gaussian distribution shown below. However, while this can be a useful measure of dispersion, it is only so if based on “statistically significant†number of samples from a large population that is normally distributed. Almost no one shoots a long enough string of shots to constitute a “statistically significant†number of samples. Just the barrel heating and fouling limits the number of shots that can be considered significant. Nor do many shooters plot histograms of the data to see if the distribution is any where near normal.
In the spirit of the original question and since I'm on the soap box, two other terms are tossed around quite casually on these forums - accuracy and precision. For clarification as applied to shooting please the attached PDF file.
In the spirit of the original question and since I'm on the soap box, two other terms are tossed around quite casually on these forums - accuracy and precision. For clarification as applied to shooting please the attached PDF file.
Attachments
Thanks guys.
Similar threads
- Deleted noremaximus
- Reloading Forum (All Calibers)
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.