3. Numerical variables
Key iNZight skills addressed:•••

Visual displays (histograms and boxplots) and summary tables (statistics) for a numericalvariable.
Use of colour to consider association with another variable
Changing between dotplots and histograms

Relevant StatsTuneUp video to consider:••‘Random Variables’ available at http://statstuneup.com.au/random-variables/‘Visual Displays: Single Variable’ available at http://statstuneup.com.au/one-variable/

Side note: Numerical variables
A variable is a measure of interest, e.g., time to download video game (in seconds). Variables may be
numerical or categorical.
Numerical variables have responses (observations, or data) that arise from a measuring process whichquantifies the outcome numerically, e.g., length (in metres), time (in seconds), weight (in kg), and so forth.
We collect data for each variable and want to describe (summarise) the information visually (throughgraphs) and quantitatively (through statistics, e.g., mean, median, range, quartiles, standard deviation).
Recommended viewing: please consider the 4-minute animated videos ‘Random Variables’ and ‘VisualDisplays: Single Variable’ available at http://statstuneup.com.au/random-variables/ andhttp://statstuneup.com.au/one-variable/ (click on ‘The Video’ tab to view)

INSTRUCTIONS
Load the nhanes_1000 dataset into iNZight using File > Example data …. You will find the data set
in Module (package) FutureLearn. See earlier worksheets if unfamiliar with this step.
Click View Variables.
Make dot plots from your numerical variables•Drag the variable name Pulse into the Variable 1 slot.

Displaying Numerical Variables using iNZightPage 1 of 5•Click Get Summary to get the associated summary table.

ASIDE: PRACTICE (~2 min)Drag the names of some other numerical variables into the Variable 1 slot - ensure you can getsimple graphs and tables like the above quickly for each variable.

Displaying Numerical Variables using iNZight

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Colour by another variable•Having ‘Pulse’ variable in Variable 1 slot, click on the Add to Plot icon at the bottom right –beneath the plot window•

Customise plot appearance is chosen by default. Under Colour by choose Age.

Displaying Numerical Variables using iNZight

Page 3 of 5ASIDE: PRACTICE (~2 min)1. While you have the Customise Plot Appearance command window active, experiment with:o decreasing and increasing the Point Size;o changing the Colour Palette;o changing the Colour by variable; ando changing each of the other control settings in this window
to see what they do.
2. Try some other choices for the numerical variable in the Variable 1 slot and the colour-byvariable.

Change between dot plots and histograms•Beneath General Appearance (beneath Add to Plot - Customise Plot Appearance), change
Plot type from dot plot to histogram.

Displaying Numerical Variables using iNZight

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Troubleshooting•

I resized the window and my plot disappeared.
 Click the Redraw plot icon (you can hover over the icons to see what they do).

•I see some columns of dots that look like they are suspended in mid-air.
 iNZight stacks points that are close together but not identical. This problem occurs
when the points are discretely spaced but too big to drop down onto the axis. Reduce
the Point size until they drop down.

•I get gaps in my histogram, why is this happening?
 Gaps in a histogram occur in intervals where there is no data. Whether or not you seethem depends on bar width which you can adjust using the Histogram bar widthslider.

•How do I change the plot title or axis labels?
 In Add to Plot select Axes and labels.

•How do I save my graph from iNZight for use in another document?
 Click on the Save Plot icon at the bottom of your graph, or go Plot > Save Plot. Severalformats are available, e.g. pdf, png.

•How do I copy and paste my graph from iNZight into another document?
 Copy and paste only works in Windows. (Otherwise you have to use screen shots.)
Click on the New graphics window icon at the bottom of your graph (you can hoverover the icons to see what they do), then you will have another copy of your graph in a
separate graphics window. Right click on this new window, and Copy as bitmap. (Copyas metafile is not working for dot plots.) The ‘snipping tool’ available to Windows users is also useful.

Additional:• for how to instructions for iNZight you should consult iNZight’s User Guides.
• for technical issues with running iNZight, you should first consult iNZight’s frequently asked
questions (FAQ) page and if the answer you need is not there ask at iNZight support.

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