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standard
In statistics, the standard deviation (SD, also represented by the lower case Greek letter sigma σ for the population standard deviation or the Latin letter s for the sample standard deviation) is a measure that is used to quantify the amount of variation or dispersion of a set of data values. A low standard deviation indicates that the data points tend to be close to the mean (also called the expected value) of the set, while a high standard deviation indicates that the data points are spread out over a wider range of values.
The standard deviation of a random variable, statistical population, data set, or probability distribution is the square root of its variance. It is algebraically simpler, though in practice less robust, than the average absolute deviation.
A useful property of the standard deviation is that, unlike the variance, it is expressed in the same units as the data.
In addition to expressing the variability of a population, the standard deviation is commonly used to measure confidence in statistical conclusions. For example, the margin of error in polling data is determined by calculating the expected standard deviation in the results if the same poll were to be conducted multiple times. This derivation of a standard deviation is often called the "standard error" of the estimate or "standard error of the mean" when referring to a mean. It is computed as the standard deviation of all the means that would be computed from that population if an infinite number of samples were drawn and a mean for each sample were computed.
The standard deviation of a population and the standard error of a statistic derived from that population (such as the mean) are quite different but related (related by the inverse of the square root of the number of observations). The reported margin of error of a poll is computed from the standard error of the mean (or alternatively from the product of the standard deviation of the population and the inverse of the square root of the sample size, which is the same thing) and is typically about twice the standard deviation—the half-width of a 95 percent confidence interval.
In science, many researchers report the standard deviation of experimental data, and only effects that fall much farther than two standard deviations away from what would have been expected are considered statistically significant—normal random error or variation in the measurements is in this way distinguished from likely genuine effects or associations. The standard deviation is also important in finance, where the standard deviation on the rate of return on an investment is a measure of the volatility of the investment.
When only a sample of data from a population is available, the term standard deviation of the sample or sample standard deviation can refer to either the above-mentioned quantity as applied to those data, or to a modified quantity that is an unbiased estimate of the population standard deviation (the standard deviation of the entire population).
Looking to sell my brand new 0Z9 to put towards a Staccato. I haven’t put one round through this thing. I’ve always wanted a Staccato and I regret not saving a little more to get one.
I have a Holosun 507c Vulcan mounted, and I can include it for a total of $1800. $1500 without.
Up for sale are 2 bricks of CCI standard Velocity Ammo, purchased directly from CCI summer of 2021.
I have kept these as spare ammo for my NRL22 competition, but have been shooting SK exclusively.
Would prefer to sell both bricks together, and priority given to members who can meet face to...
Walnut stock M1A in 308 had about 300 rounds through it got some brass kisses and a couple knicks but nothing serious on it. Comes with the factory 10 round mag, 420 round checkmate mags, rifle bag and literature included. Only disassembled once to apply grease and apply a couple coats of...
I have both halves of an ar15 in 5.56 as marked on 16" barrel. No branding evident on the upper, railed gas block, MPI BCG, no branding either. Like new. Has ruger polymer front sight and carry handle but the sights dont line up. i think you need either a spacer for the front or a fixed iron...
Can Washington residents buy handguns with standard capacity magazines if they purchase them in the state of Oregon? I don’t know the intricacies of gun laws in Washington. Asking for a friend.
Winchester Large Rifle Primers for Standard Rifle Loads
$95
No shipping /// Haz-mat
Face to Face FTF Fishers Landing Fred Meyer on se 164th Av East Vancouver ///// Or if we can meet up when I'm out and about I like to make easy if I can.
Texting is easiest and fastest if you are interested...
Brand new blued upper with case
This is interchangeable with any other standard Mk IV frame.
(not sure about the 1911 framed ones though)
Just take the bolt from your other upper and swap it and it's good to go.
This is the primary serialized piece of the Ruger MK IV so it is considered a...
I have 6 bricks of CCI Standard Velocity LR for sale. Price is $45 per brick. Each brick contains 10 boxes of 50 rounds for a total of 500 rounds per brick. I would sell all 6 bricks together for $260.
Gen 2 6.9” threaded barrel, will include everything except the lower as it has already sold. Looking to get $800 out of it (lowers usually run between three and four hundred). In great shape, only take to the range one time (about 200ish rounds). Small chip on Handguard finish from crappy B&T...
Looking to trade this RIA 1911 with another pistol or a lever action rifle. If you have any other interesting trade feel free to send a PM and ask. I would prefer to trade with another firearm though. Comes with the box and 3 8-round magazines, one factory two others I purchased later.
Target Sports USA has CCI Standard Velocity 22lr 40gr lead round nose for $400 for 5,000 with free shipping and handling. If you have their prime membership ($95 a year) it's $367.91 for 5,000...
Rock Island M1911-A1 CS
45ACP - 3.5” Barrel
1 - 7 Round Magazine
Hogue Wraparound Grips w/Finger Grooves
Kydex OWB holster
100 rounds Winchester Target Ammo
10 rounds Hornady Critical Defense Ammo
No box or manual
Gun is in excellent condition.
I took this in trade a while back so I don’t know...
Hi there,
For sale here is my Browning Buck Mark URX .22LR pistol. Original owner, no issues, shot infrequently and in great condition. It's a very accurate .22LR pistol, which is why I purchased it. Would keep it but am looking for a .22LR suppressor host so this is funding that search...
Taken on one range trip, worked excellent but need money for other things at the moment. Has minor cosmetic wear in end plate from previous brace installation along with a small chip on the finish of the top rail from where the front sight sits, but aside from that it is in perfect shape. Does...
the last generation of these GI style mags as the company is stopping production. lightweight and very nice feeding. these are new, and come sealed. Local pickup only.