While we have made these apps easily and freely accessible (no prior permissions required for download or use, and no central data collection for which you must gain access), we do recommend that all data collectors be trained in their proper use. This typically involves an hour or two of face-to-face workshop talking about the apps, their aims, the role of the data collector, common and uncommon occurrences in the field and submitting/checking data. It is also preferable that prior to data collection, data collectors have the opportunity to practice administration of the apps with an appropriately aged child, with a more senior data collector providing feedback. This will help ensure standardisation of fieldworker responses, sufficient engagement of the fieldworker during data collection, and ensure they are not 'over-helping' during data collection. For those with more experience working with young children and administering psychological measures, this training can be reduced.