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Welcome to Epi Info 7 training.
In this video
you'll get an overview of performing a 2x2 Table analysis
in the Visual Dashboard.
You should use 2x2 tables when you're looking for an association
between a binary exposure
and a binary outcome.
Such as if a person ate a certain food or not
or if they got sick or not.
You're looking at a spreadsheet of the data we collected on a fictitious
foodborne illness investigation.
Each row represents a single person
and the columns indicate
if the person became ill
and if they consumed a variety of foods.
We'll use this dataset to run the 2x2 table analysis.
Now I'll close the spreadsheet and go to the Visual Dashboard in Epi Info 7.
I've already set the data source
in Epi Info 7 as you can see here at the top of the page.
Now we'll use a 2x2 table analysis to test each food exposure for
an association with being ill.
I'll right-click on the dashboard and go to the 2x2 table analysis gadget
and I'll choose exposure and outcome.
Of course the outcome is ill
and the exposure, we'll just use the top of the list, Ham,
and run the analysis. Looking at the output, the quadrants here on the left
show that 26% ate ham and got ill, 40% didn't eat ham and
still got sick. So let's look at the next variable. We'll do another 2x2
table
on the next item in the list.
So our outcome is ill
and our exposure is lettuce.
This time 52% of the lettuce eaters got ill.
Since this is a high probability of being a vehicle for the illness
let's look at the odds ratio.
It's 5.5 and since it's lower confidence limit is greater than
1, this allows us to say that lettuce
is associated with illness.
But we still have quite a few foods left on our list and we need to look at each
one.
It would be tedious to do a 2x2 table for each one so I'll define a
variable group which allows me to take a short cut.
Mouse over the defined variables tab on the left side of the dashboard,
click New variable, and at the bottom I'll click Create Variable Group.
I need to name the group, I'm going to call this Foods.
I'll need to highlight each item
by holding down the shift key
and then click OK. Now by right-clicking on the dashboard I can do a 2x2
analysis on the entire group. My outcome is still ill.
However in exposure,
I can use my Foods group
and click Run.
And now I have
a 2x2 analysis on every food in the group.
Not only do I have ham, but lettuce
and mayonnaise and,
all the other items.
In addition to that I also have a summary at the very top left.
I can click on the top of each column and it'll sort the items for me.
Now I can see that in addition to lettuce, both tomato and onion have odds ratios
greater than 1.
We have three foods that are candidates as the vehicle for the illness.
Thanks for watching and you'll get more detail from future user support videos.