[ 3 / biz / cgl / ck / diy / fa / g / ic / jp / lit / sci / tg / vr ] [ index / top / reports / report a bug ] [ 4plebs / archived.moe / rbt ]

Maintenance is complete! We got more disk space.
Become a Patron!

/sci/ - Science & Math

View post   

[ Toggle deleted replies ]
File: 448 KB, 588x391, 1560656149090.png [View same] [iqdb] [saucenao] [google] [report]
11194800 No.11194800 [Reply] [Original] [archived.moe]

Hello, stats question please. Confidence intervals.

Let's say I have 5,000 daily values in a time series, and that the sample standard deviation of those 5,000 values is 10, with a mean of, say, 0.

I would say that, with 90% confidence, the next day's value will be between -10 and 10, right?

But I had this discussion with someone who says that you need to divide the SD by sqrt(5000-1), -> (-.14, .14)

I of course know the formula that they are using, but I forget why and when that's used, seems retarded here. What's going on? pic is dog

>> No.11194807
File: 80 KB, 586x690, TRINITY___their_foot_will_slip.jpg [View same] [iqdb] [saucenao] [google] [report]

The Israelites forsook the Lord and turned to the whore of Babylon instead.

>> No.11194811

Yes I know that now please let's discuss something that isn't completely obvious.

>> No.11194842
File: 47 KB, 702x937, TIMESAND___536u56hbds.jpg [View same] [iqdb] [saucenao] [google] [report]

I think mathematicians should entertain the notion that the point density of abstract mathematical points is infinity points per point rather than the one point per point which is commonly assumed. What is your opinion?

>> No.11194846

Our opinion is that infinity is the shared point of reflection for all algebraic geometry, or word salad potato monkey.

>> No.11194855

I will take away your blessings.

>> No.11194859

What blessings? I'm Satan. I don't have any blessings. Pretty sure you can't demote me to anything less than Satan at this point, God, unless you don't want to have someone to put in your magical 'timeout' room.

>> No.11194861
File: 391 KB, 2048x2021, 1573168707924.jpg [View same] [iqdb] [saucenao] [google] [report]

You're both wrong, but your friend is closer. When determining the margin of error, you divide the standard deviation by the square root of the sample size, not the sample size -1. Also, you multiply that by the z-score that corresponds to your give confidence interval. For 90%, that's 1.645. Then you add and subtract that product from the mean.

>> No.11194862

If the values are normally-distributed, then the 90% confidence interval for the next value will be ±10*Z_0.95 = ( -16.45, +16.45)

>> No.11194866

If there weren't things in the world that you care about, things that I can take away from you and use to hurt you with, then you wouldn't be in these threads. If you had nothing, you wouldn't care.

>> No.11194883

Why would that be the conclusion I reach, you fucking retarded American mongoloid?

>> No.11194891

Just like me, you make those posts you make because you want someone to like what you write.

>> No.11194893
File: 37 KB, 480x270, giphy-facebook_s.jpg [View same] [iqdb] [saucenao] [google] [report]

>Watch how Tooker's rage boner increases 500%!

>> No.11194899 [DELETED] 

i'm 12 whats happening

>> No.11194904

>whats happening
two retards decided to have a pissing contest in a statistics thread

>> No.11194905

Huh? Wow, how much self-esteem do you NOT have there Tooker? Serious question.

>> No.11194907

Statistically speaking, all threads are Tooker threads.

>> No.11194920

Even if you are ready to pay the price I will extract from you, your loved ones certainly are not ready to pay it in kind.

>> No.11194923

oh shit is this true? am i retard?

>> No.11194925

The Sicilian kike!

>> No.11194926

you just weren't paying attention

>> No.11194951

Its (-.233, .233).

>> No.11194961

well for real though, what is the interpretation of the mean +/- z*std/(sqrt(n-1)) when we are looking at drawing one additional datapoint? Maybe the interpretation is something like, if we draw "n" additional datapoints, then their average would be within that interval 90% of the time or whatever. But if the true standard deviation is 10 (mean 0) then I feel like, well okay yeah for 90%, z*10 -> (-16.45, 16.45) makes sense. But I don't see when the fuck you would divide the SD by 5000 or whatever. However that's a mainstream formula...

>> No.11194966
File: 105 KB, 620x460, 620c3b22ab2fa50849727b03eeaaf53a92cae398ea83e789e09258055d7d02a6.jpg [View same] [iqdb] [saucenao] [google] [report]

Since when was I loved? This is news to me. May I know who this person(s) is/are?

>> No.11194967 [DELETED] 
File: 124 KB, 244x246, new.png [View same] [iqdb] [saucenao] [google] [report]

a literal schizophrenic argues with the LORD of /sci/

>> No.11194971
File: 41 KB, 800x450, oogaboogaaa.jpg [View same] [iqdb] [saucenao] [google] [report]

A literal autistic sociopathic schizophrenic argues with the magic cave wall that moves and shimmers as the rain falls washes away all the paintings I, Ug the caveman, made.

>> No.11194980
File: 93 KB, 721x614, ayapuhls .png [View same] [iqdb] [saucenao] [google] [report]

Okay I get it now. Thank you apples you are my greatest ally. Basically i'm right. Yeah, with 5000 observations, and a sample mean of zero and a sd of 10, yeah we would estimate the true mean to be like ( >>11194951 ) what you said with 90% confidence.

Okay that makes sense.

But what I am talking about is, if we are to draw one more piece of data, what is a 90% CI of its expected value? Okay and that is -16,16? That seems reasonable too.

Okay pack in up I think we're done thanks for entertain.

>> No.11194981

Where are you even getting that first form of it? You always divide by the square root of the sample size, because using a larger sample size allows you to be more accurate. Imagine using a sample size of 3: your interval would become (-9.527, 9.527). It's still a 90% confidence interval of a normally distributed population with a standard deviation of 10, but because the sample is so much smaller, the interval is wider, meaning less precision.

>> No.11194984

No, you would use the same formula but with a sample size of 5001.

>> No.11194985

>reddit spacing
paypal me or find me on Chegg - Phil F

>> No.11195009
File: 60 KB, 582x449, 1520257701316.jpg [View same] [iqdb] [saucenao] [google] [report]

The sample standard deviation is already divided by the square root of the sample size.

>> No.11195037

What is a square root supposed to indicate from the logic of perspective? Does irrational = shared?

>> No.11195046

No it’s not. It’s the square root of the sum of the squares over the sample size.

>> No.11195060

same thing tho unironically?

>> No.11195810
File: 203 KB, 500x458, 1574402568135.jpg [View same] [iqdb] [saucenao] [google] [report]

It helps if you know what standard deviation represents, as well as how to calculate it. You find the difference between each datum and the mean, square the difference to make them all positive, then divide by the sample size. This gives you the variance, which represents to total variation of your sample. Taking the square root of the variance gives you the standard deviation, which is the average difference any datum is from the mean.

Going back to confidence intervals, you further divide the standard deviation by the square root of the sample size before multiplying with the z-score. Why? Because you can arrive at the same standard deviation with two samples of wildly different sizes. The larger your sample size, the more precise you can be in determining the 90% CI. See >>11194981
>Imagine using a sample size of 3: your interval would become (-9.527, 9.527). It's still a 90% confidence interval of a normally distributed population with a standard deviation of 10, but because the sample is so much smaller, the interval is wider, meaning less precision.

>> No.11195827
File: 990 KB, 1312x988, TIMESAND___ZZ0p9f8ig3y35hy5y35yffiZrthrthZfuZZhwthwththwrekyj56ufjf3tf.png [View same] [iqdb] [saucenao] [google] [report]

>> No.11197135

You should have to pass a test to post here.

>> No.11198179
File: 238 KB, 1205x2085, TIMESAND___Exide+Strzok+insurance+policy.png [View same] [iqdb] [saucenao] [google] [report]

I wonder at times if the Strzok "insurance policy" was that Exide inserted into my 2016 hiring paperwork fraud papers saying that I have authorized them to drug/rape/hypnotize/censor/torture/kidnap/mutilate me as much as they want, or that the job I was being offered was something other than the lowest ranking SQL bitch in the IT department of manufacturer and vendor of electrical batteries. Although all of the conditions of fraudulent misrepresentation are plainly met:
>The Elements of Fraudulent Misrepresentation
>In order to prevail in a lawsuit for fraudulent misrepresentation, the plaintiff must be able to prove the following six elements:
>A representation was made (in contract law, a representation is any action or conduct that can be turned into a statement of fact)
>The representation was false
>The representation, when made, was either known to be false or made recklessly without knowledge of its truth
>The representation was made with the intention that the other party rely on it
>The other party did, in fact, rely on the representation.
>The other party suffered damages as a result of relying on the representation
I would not be surprised at all to learn the the USA courts have determined that Exide's fraud contract is valid because their conspiracy to defraud me did bear the fruit of my signature on their fraud contracts when I signed them in good faith after they were represented to me as being related to the terms of employment I discussed. Furthermore, I would not be surprised in the least to learn that Chief Justice John Roberts himself was the one who made to me these fraudulent misrepresentations when he told me the hiring paperwork was related to the terms discussed: 40hrs of SQL-themed bitch work for an electrical battery manufacturer and absolutely nothing to do with me authorizing them to drug/rape/hypnotize/censor/torture/kidnap/mutilate me.

>> No.11199693
File: 134 KB, 276x512, TIMESAND___777777766666622doge.png [View same] [iqdb] [saucenao] [google] [report]


Name (leave empty)
Comment (leave empty)
Password [?]Password used for file deletion.