Specifying Default Level for a Factor in Linear Regression

ijourneaux

Just found JASP and starting to dive in. Looks like a great tool and looking forward to becoming more proficient.

When doing a linear regresion with a factor, is it possible to specify which level is the default? For example, in the Titanic sample dataset, I would like to make the default passenger Class to 3rd class instead of 1st class. A related question; when looking at the linear regression results, how do you know which level was used as the default?

patc3

1) changing the reference category:

In the data view, click on the variable name, the reference category will be the first value at the top. To change the order of the values, you can select a row and use the up and down arrow. So you can put the category you want as reference at the top (in this example, I want Non at the top):

View gif animation here

https://i.imgur.com/3JTLELn.gif

2) how to know which level was used as the reference category:

In the regression output, the reference category is the only category not shown in the list effects (here, Non is not shown, so it's the reference category). Of course you can always go back to the data view as above, click on the variable name, and look at which category is at the top.

ijourneaux

Merci!