Summary on Notation
Notation Recap
Notation is an essential tool for communicating mathematical ideas. We have
introduced the fundamentals of notation in this lesson that will allow you to
read, write, and communicate with others using your new skills!
Notation and Random Variables
As a quick recap, capital letters signify random variables. When we look
at individual instances of a particular random variable, we identify these
as lowercase letters with subscripts attach themselves to each specific
observation.
For example, we might have X be the amount of time an individual spends on
our website. Our first visitor arrives and spends 10 minutes on our website,
and we would say \bold{x_1}x1 is 10 minutes.
We might imagine the random variables as columns in our dataset, while a
particular value would be notated with the lower case letters.
Notation English Example
Time spent
X A random variable
on website
First observed value of the random
x_1x1 variable X
15 mins
Sum values beginning at the first 5 + 2 + ... +
\sum\limits_{i=1}^nx_i i=1∑nxi observation and ending at the last 3
Sum values beginning at the first
\frac{1}{n}\sum\ observation and ending at the last (5 + 2 +
limits_{i=1}^nx_in1i=1∑nxi and divide by the number of 3)/3
observations (the mean)
Exactly the same as the above - the (5 + 2 +
\bar{x}xˉ mean of our data. 3)/3
Notation for the Mean
We took our notation even further by introducing the notation for summation \
sum∑. Using this we were able to calculate the mean as:
\bold{\frac{1}{n}\sum\limits_{i=1}^nx_i} n1i=1∑nxi
In the next section, you will see this notation used to assist in your
understanding of calculating various measures of spread. Notation can take
time to fully grasp. Understanding notation not only helps in conveying
mathematical ideas but also in writing computer programs - if you decide you
want to learn that too! Soon you will analyze data using spreadsheets. When
that happens, many of these operations will be hidden by the functions you
will be using. But until we get to spreadsheets, it is important to understand
how mathematical ideas are commonly communicated. This isn't easy, but
you can do it!