| df_pisa18 | PISA 2018 Student questionnaire Database |
| df_talis18 | TALIS 2018 Teachers Database |
| est | Estimate list |
| grouped_sum_freqs | Grouped Frequencies |
| grp | grp |
| inv_test | inv_test |
| n_obs_x | Number of observations valid for column x |
| Rrepest | Rrepest |
| weighted.corr | Weighted Bivariate Correlation |
| weighted.corr.cov.n | Multivariate Correlation and Covariance |
| weighted.cov | Weighted Bivariate Covariance |
| weighted.iqr | Weighted Interquantile Range |
| weighted.quant | Weighted Quantile |
| weighted.std | Weighted Standard Deviation |
| weighted.var | Weighted variance |