Study Notes #3

Notation and Random Variables

• capital letters - random variables
• lowercase letters with subscripts - individual instances

Notations

X
A random variable
Example - Time spent on website
(On spreadsheet the column label)</code></pre>
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x1
First observed value of the random variable X. (subscript row number)
Example - 15 minutes</code></pre>
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\sum_{i=1}^nx_i


Sum values beginning at the first observation and ending at the last value
Example: 
5+2+3</code></pre>
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\frac 1 n \sum_{i=1}^nx_i


Sum values beginning at the first observation and ending at the last value and divide by the number of observations (the mean)
Example:
(5+2+3)/3</code></pre>
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\bar x


Exactly the same as the above - the mean of our data.
Example:
(5+2+3)/3</code></pre>
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Notes for Spreadsheet


Range:


=A1-AVERAGE(A$1:A$10)


same with:


x_1-\bar x


=C1^2
square root for each data of a data set in spreadsheet
get the average to get the variance</code></pre>
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I think, the formula can also be written as:
=(A1-AVERAGE(A$1:A$10))^2
=AVERAGE(D1:D10)</code></pre>
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Testing my theory...





Shape and Outliers






https://docs.google.com/spreadsheets/d/1HHDUL0vK9zFAh1FekwWQy4rrL4pyKS0WBq8kicG8e3Q/edit?usp=sharing






Suggested Reading from my first project's feedback: 


What are headings and why are they important?
How to write descriptive headings
Data Journalism Handbook - Using Data Visualization to Find Insights in Data