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I am writing a program for an assignment in which I need to incorporate these two formulas; but, the problem is, I have no understanding of the formatting of these formulas and I am just at a loss with what I could find online.

Maybe the question I should be asking is, "What kind of formatting is being used for those formulas and what does each part mean?"

I apologize for lack of clarity and for my confusion -- I've been dealing with trying to figure this out for weeks, on and off, and use Stack Exchange as a last resort.

Below is a screenshot attachment.

Formulas

Edit: And I did see this other post, but it confuses me. I haven't made it that far in math.

miracle173
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John Doe
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  • This wikipedia article about summation may help understand the formulas. – Gribouillis Oct 16 '17 at 07:54
  • Just out of curiosity, are you still a high school student? – 5xum Oct 16 '17 at 07:55
  • Thank you, Gribouillis.

    @5xum: I graduated high school last year; but, unfortunately, we only touched up on it very briefly at the end of pre-calculus. We haven't used it in math so far at my university, either.

     – John Doe Oct 16 '17 at 08:03
  • @JohnDoe I see. Because summation (and summation notation) is something that's usually covered in high school (or at least it should be). – 5xum Oct 16 '17 at 08:04

2 Answers2

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In mathematics, $\sum$ often means "sum", and the term

$$\sum_{i=1}^n a_i$$

is read as "the sum of all $a_i$ where $i$ goes from $1$ to $n$, in other words

$$\sum_{i=1}^n a_i = a_1 + a_2 + \cdots + a_n$$

5xum
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  • Thank you very much! Your answer, and Yves Daoust's answer, helped me a lot and solved my problem, thank you guys very much! – John Doe Oct 16 '17 at 08:07
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The formula for the mean means that you need to take the sum of all values and divide by the number of values.

The second says that you take the sum of the squares of the values, divide by the number of values and subtract the square of the above mean.

  • Thank you very much! Your answer, and 5xum's answer, helped me a lot and solved my problem, thank you guys very much! – John Doe Oct 16 '17 at 08:07