OK, assuming everything is now good with our variable setup, let’s get on with it!
The basic way to make a table or crosstab, is to select a variable in the Accordion, and then drag another variable on top of it.
- Go to the Accordion, and select Internet Usage at Home.
- Go to the Accordion, open Time & Geography and locate Country. Notice the cursor changes to the open hand icon when you hover over it.
- Left-click and drag Country over to the right… without letting go (yet)
Notice how the screen changes in the Main Area with lots of different rectangular slots.
- Drag Country and drop it into a slot that will put it as the columns. It may say “Country as Columns” or “By Country”
And then you should have a crosstab of Internet Usage by Country.
We can sort the table using the column headings.
- Click UK in Country on the table to sort it by that column
At the bottom of the screen is the Display Controller. It has lots of options to help you change the look of your table.
Let’s start by looking at the chart types. Crunch will only display chart types that are appropriate to the table you are working with (so you can't make a crosstab into a donut chart).
- Change to each of the various chart types, including the stacked bar and column charts
- Turn back to a table
You can also change the statistics in the table.
Most typically, researchers want to change between the Counts (N) and the Percentages (%) - but there’s also the Z-score and Index available on crosstabs.
- Change to the Count (N)
- Change back to the percentages (%)
The next button across is an arrow which tells us which direction percentages are calculated (rows or columns).
The default is the down-arrow, which means the percentages are column percentages. That is 79.9% of China are Over an hour a day.
But we can change that. If we did the horizontal arrow, it would become a row percentages. In this example, 20.1% of those who are Over an hour a day are Chinese. Typically, you want the down arrow because the explanatory variables are along the top. The square box icon means a total percentage (of the valid sample in the table).
- Click through all percentage-direction options to see the differences
Next, the asterisk * icon turns the default statistical testing on and off.
- Turn on hypothesis testing
Where the cells in the table are now shaded according to this legend in the lower-left corner of the screen.
Note as well a scale legend key opens down the bottom left.
To explain (briefly):
- Researchers are often just used to seeing a p-value of 0.05, but here we see a scale. The darker the color, the smaller the p-value that is, the more confident we are.
- The direction of the magnitude is done by color. Green cells are greater than what we'd expect, and red are less than what we'd expect.
- This hypothesis testing is based on the Z-score, and takes into account the whole table (ie: row and column expectations).
- For more information, you can read here.
Whereas this default coloring gives a view of the overall difference between rows and columns, sometimes we just want to compare everything to a specific column. For example, let’s say we want to compare everyone to Germany.
- Hover the mouse directly under the column of Germany
- Notice it says Set Comparison underneath the column
- Click this to set comparisons
Now it's comparing Germany to everything else.
(Note to instructor: Point out any significant differences between your set column and anything else and explain the degree of significance. In example above, it’s comparing the 19% for Germany to the 23% for China, and China in this case is statistically higher at the 0.1 level).
Let’s try a different column to compare to.
- Click underneath France to Set Comparison
Clicking again underneath the column, resets the comparisons to the whole table
- Click again under France to Reset. Notice it resets the stats testing to what we saw earlier (the whole table).
Now turn off hypothesis testing altogether.
- Click on the asterisk * in Display Controller
Now let’s change the precision of the decimals.
- Change to two decimal places, and to one, and then back to no decimal places.
Next, the double arrows button allows you to switch the rows/columns for a table or chart.
- Click on the double arrows button.
We now have Country on the rows and Internet Usage at Home along the top
- Click again to switch back to the former state.