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CHRONOGRAPHS, ES AND SD (Read 1452 times)

joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	CHRONOGRAPHS, ES AND SD Nov 6^th, 2018 at 8:39am	Print Post
	9 CHRONOGRAPHS, ES AND SD Chronographs, used to measure bullet speed, commonly calculate Muzzle Velocity or MV of each shot; and the Average, Extreme Spread or ES, and Standard Deviation or SD of a set of shots. We test a sample to estimate values of the population, of values of a zillion shots. We sometimes see unusual numbers while chronographing, with MV being very high or low for some shot/s compared with the other shots in the set. We can examine a test by dividing ES / SD and checking the table. Sets of n shots will have ES / SD less than the table values 97% of the time. So, we are 97% sure that a set of shots, with ES / SD GREATER than the table value, does NOT have Average, ES and SD that are representative of the population. If a set of n = 10 shots has ES / SD greater than 4.67; then we are 97% sure that something is amiss. Increasing the number of shots, n, may bring ES / SD down.


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Dellet Frequent Elocutionist Offline Posts: 1303 Joined: May 19^th, 2017	Re: CHRONOGRAPHS, ES AND SD Reply #1 - Nov 6^th, 2018 at 4:19pm	Print Post
	joeb33050 wrote on Nov 6^th, 2018 at 8:39am: 9 CHRONOGRAPHS, ES AND SD Chronographs, used to measure bullet speed, commonly calculate Muzzle Velocity or MV of each shot; and the Average, Extreme Spread or ES, and Standard Deviation or SD of a set of shots. We test a sample to estimate values of the population, of values of a zillion shots. We sometimes see unusual numbers while chronographing, with MV being very high or low for some shot/s compared with the other shots in the set. We can examine a test by dividing ES / SD and checking the table. Sets of n shots will have ES / SD less than the table values 97% of the time. So, we are 97% sure that a set of shots, with ES / SD GREATER than the table value, does NOT have Average, ES and SD that are representative of the population. If a set of n = 10 shots has ES / SD greater than 4.67; then we are 97% sure that something is amiss. Increasing the number of shots, n, may bring ES / SD down. I must be really slow in the brain works department today. Can you show an actual example? Am I missing something obvious? Otherwise an ES of 50 with an SD of 9 looks acceptable in a sample of 35 or more shots, 50/9=5.55. While ES50/SD8=6.25 is not


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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: CHRONOGRAPHS, ES AND SD Reply #2 - Nov 6^th, 2018 at 4:48pm	Print Post
	Dellet wrote on Nov 6^th, 2018 at 4:19pm: joeb33050 wrote on Nov 6^th, 2018 at 8:39am: 9 CHRONOGRAPHS, ES AND SD Chronographs, used to measure bullet speed, commonly calculate Muzzle Velocity or MV of each shot; and the Average, Extreme Spread or ES, and Standard Deviation or SD of a set of shots. We test a sample to estimate values of the population, of values of a zillion shots. We sometimes see unusual numbers while chronographing, with MV being very high or low for some shot/s compared with the other shots in the set. We can examine a test by dividing ES / SD and checking the table. Sets of n shots will have ES / SD less than the table values 97% of the time. So, we are 97% sure that a set of shots, with ES / SD GREATER than the table value, does NOT have Average, ES and SD that are representative of the population. If a set of n = 10 shots has ES / SD greater than 4.67; then we are 97% sure that something is amiss. Increasing the number of shots, n, may bring ES / SD down. I must be really slow in the brain works department today. Can you show an actual example? Am I missing something obvious? Otherwise an ES of 50 with an SD of 9 looks acceptable in a sample of 35 or more shots, 50/9=5.55. Correct! While ES50/SD8=6.25 is not. Correct! Your examples are correct.


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Dellet Frequent Elocutionist Offline Posts: 1303 Joined: May 19^th, 2017	Re: CHRONOGRAPHS, ES AND SD Reply #3 - Nov 6^th, 2018 at 5:12pm	Print Post
	So, 50/8.75=5.72 would be marginal in a 50 shot string. 50/9=5.55 looks pretty good. 50/32=1.56 looks the same as, if not better than. 11/7=1.57 How do you attach a little better meaning to those numbers?


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