| Group assignment |
Deterministic. Participants assigned to groups based on tutor group membership |
Quasi-, stratified randomization. Participants assigned to groups on a quasirandomized basis (children with visual anomalies not assigned to the visual frequency discrimination group), stratified according to gender, year group (year 4 versus year 5), and native-English status |
| Existence of a control group |
No-intervention control group only |
No-intervention control group; auditory training control group; visual training (placebo) control group |
| ‘Blindness’ of (a) participants; (b) experimenters to group membership |
Neither (a) participants nor (b) experimenters blind to group membership |
(a) Participants in three training groups (phoneme discrimination group; auditory frequency discrimination group; visual frequency discrimination group) blind to training group membership. Participants in the no-intervention group not blind no-intervention status. (b) Experimenters not blind to group membership of participants |
| Blindness of experimenters to pretraining scores at posttraining |
Experimenters not blind to pretraining scores at posttraining |
Experimenters blind to pretraining scores at posttraining |
| Similarity of treatment of trained and no-intervention groups |
Phoneme discrimination group, but not no-intervention group, rewarded with prizes |
Both phoneme discrimination and no-intervention groups rewarded with prizes |
| Experimenter familiarity |
Phoneme discrimination group familiarized with experimenters at pre- and post-training and during training. No-intervention group familiarized with experimenters at pre- and post-training only |
Phoneme discrimination group familiarized with experimenters at pre- and post-training and during training. No-intervention group familiarized with experimenters at pre- and post-training, and during training for ∼5 min per week on a group basis and 9 times per week during participant collection |
