Mathematics Questions

>>8112928

start with more basic stuff then if you dont understand what the course expect you to understand already. the reversed E is summing all the xi 's from 1 to n

>>8112936
What is the x with that line on top of it?

>>8112956

its the mean, anon.

>>8112958
So, the backward E n i = 1 thing, means that i sum all of the (xi - mean)^2.
Where do i find documentation regarding backward E n i = 1

>>8112968

yea , sum up all the squared deviations from the mean

http://www.mathsisfun.com/algebra/sigma-notation.html

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>>8112970
So it says the Sum goes from i=1 to n.
So we should sum up i = 1 to 201.
So it should be
s^2= [(1+2+3...201)(xi-mean)^2] / n-1

But i have a feeling i am incorrect, as this was posted in the video.

>>8112980
Yes you've done it incorrectly.
You need to sum up what's in the brackets from i= 1 to i = 201. What you've done is sum up the i instead.
Easy example:
[math]\sum^5_{i=1}x_i = x_1 + x_2 + x_3 + x_4 + x_5[/math]

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>>8112990
Ok.
So it goes.

>>8113007
Yep. For conciseness, we call the "thing to sum" the summand.
This "thing to sum" will depend on n or i or whatever letter is underneath the [math]\sum[/math].

Will cont. Tmw.
Test in eng. Tmw hav to study today

>>8112928
If you want help with your homework, go to /wsr/ - Worksafe Requests.

>>8113412
Its not homework, its a course on Coursera, a website with free online courses.

>>8113429
It's a free online circle jerk for faggots like you.

>>8112928

∃ There exists
∃! There exists a unique
∄ There does not exist
∀ For all
∑ Sum over an index
∏ Product over an index
{ ... } A set
∈ Belongs in set (is an element)
∪ Union of sets (combines all elements into a bigger set)
∩ Intersection of sets (only the elements in both set)
⊆ is a subset (elements on the left are in the set on the right)
⊊ is a strict subset (the sets aren't equal but still subsets)
∎ End of proof
∖ Set difference (remove the elements in the right set from the left set if they are there)
σ Standard Deviation
‾ Mean/Average
[math] {}^2 [/math] Squaring (multiplying it with itself)
[math] {σ}^2 [/math] Variance

>>8113461
first day of discrete math?

>>8112928
I don't get it. You're "just getting" into math, and this is the first thing you do? How much math do you already know? Why couldn't you just Google the symbol, which is also one of the math's most recognizable ones?

>>8113480
It's a troll you idiot.

>>8113512
I thought so myself, but you actually never know 100%.

>>8113461
Not OP, but that's nice of you anon.

>>8113467
Fuck off, someone's being nice and helping the OP and all you can do is attempt to be condescending?
Back to the containment zone in your basement virgin neckbeard, and take your animu figurines with you.

update: was at school (non related to mathematics)
will post something soon

Ok. So I have a quesiton.
The teacher says we are learning about quantifiying centers of numerical distributions.
So far talked about Measures of Center (which i understand) and measures of spread(which i have yet to understand fully).
I just want to know where they come up with the titling. For example if i google quantifying numerical distributions i get nothing.
But if google measures of spread i get loads of information.
Like what title does measures of spread (range, variance, standard deviation) and measures of center (mean median mode) fall under, when looked at the universal mathematics help() doc. Is there one and where do i find it, other than wikipedia. Because i just want to go straight to the source if i have a question.

>>8115536
Like is where is the official documentation for the topic of measures of spread

>>8115543
I don't know what im asking anymore

>>8115546
>>8115543
>>8115536
>>8112928
On Wikipedia it says what I'm learning is called Statistical Dispersion.

>>8115543

measure of spread is what you are calculating in your first image in this thread

its the variance. how much the data spread away from the mean.

measures of spread and measures of center falls under descriptive statistics if you want to research further.
the big E is called a sum and the top number n refers to how many numbers you are finding the variance of(201 in this example). the bottom index i=1 means you start from the number 1. so the sum notation means "sum from i=1 to 1=n.
the variance calculation tells you find the difference between the individual observation xi and the mean x bar. that number is squared to remove any possible negative variance.
so pretty much you are finding how much each observation differs from the mean and then dividing by the amount of observations. because this is a sample you divide by n-1(for a population mean you divide by n).
So what the variance tells you is how much each observation varies from the mean on average.
the sum notation saves you having to write out 201 sums.

>So it says the Sum goes from i=1 to n.
So we should sum up i = 1 to 201.
So it should be
s^2= [(1+2+3...201)(xi-mean)^2] / n-1
the 201 means the 201st observation, the i values are just place holders
s^2=(60.3-70.5)^2/200+(77.2-70.5)^2/200+...+(58.1-70.5)^2/200

hope i didnt get baited

s^2=[(60.3-70.5)^2+(77.2-70.5)^2+...+(58.1-70.5)^2]/200
meant that as the last line

/sci/, there are times when you warm my heart. I'm proud of you.

How is that symbol a "reversed" E?

"There exists" is a reversed E.

The summing symbol is a crooked E.

>>8116777
/sci/ has become nothing but "homework help" for the past two or three years.
It's literally just undergrads trying to feel smart by helping others, because everyone who actually does shit and knows anything has left.

I'm only on /sci/ like once a month anymore.

>>8117182
Do you really not see the difference between [math]\exists[/math] and [math]\Sigma[/math]?