StatsNotebook

The tutorial is based on R and StatsNotebook, a graphical interface for R.

For categorical variable, it is important to set a “reference” category in many analyses. For example, for the variable Sex in our regression analysis tutorial, the default reference is Female. The coefficient of SexMale from the regression represents the effect of male relative to female. In this case, the coefficient -0.87 means that the depression score (the dependent variable in that analysis) for male is 0.87 lower than female.

Coefficients:
                  Estimate Std. Error t value Pr(>|t|)    
(Intercept)        7.98352    3.57490   2.233   0.0270 *  
Agreeableness     -0.01498    0.02859  -0.524   0.6011    
Conscientiousness -0.01702    0.02231  -0.763   0.4467    
Extraversion      -0.02104    0.01839  -1.144   0.2546    
Neuroticism        0.14296    0.01891   7.559 3.94e-12 ***
Openness          -0.05455    0.02454  -2.222   0.0278 *  
SexMale           -0.87264    0.88739  -0.983   0.3270    

Set reference category

Changing reference category is easy. It takes only one line of code in R. Alternatively, we can set the reference with a few clicks in StatsNotebook.

R codes

currentDataset$Sex <- relevel(currentDataset$Sex, ref="Male")

Using StatsNotebook

1. Click Data at the top
2. Click Reference
3. In the column Update Reference Level, we can now set the reference category for any categorical variable.

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