The OSF project accompanies the Stage 1 Registered Report **Impact of stimulus variability on understanding of reversible sentences in children with Developmental Language Disorder: learning vs generalisation**. Here we include a number of scripts used to conduct power analysis and generate experimental items. The images required to generate items are included in the *multpic* and *experimental_images* folders. **make_pretest_2021.R**. This script creates item sets for pre- and post-test assessment. At pre- and post-test participants are provided with arrays of images and must identify which relates to a spoken sentence. The images referenced in this spreadsheet are included in the *mulitpic* folder. The output generated by running this script are included in the *make_pretest_output* folder. Mp3 files are stored in *PreTest_mp3_output*. *make item comb 2021.Rmd**. This creates 12 novel and 12 repeated items; half the sheets have sentence type 1 as novel and sentence type 2 as repeated, and the other half the opposite. The spreadsheets generate by using this script are included in the *make_items_output* folder and the sound files are under *mp3_output*. **appendix3b_treasuremain.Rmd**. This scripts details apriori power analysis for linear mixed-effects model analysis and indicates that 48 participants would be required to achieve 80% power. This was omitted in a revision of the Stage 1 report and is retained for transparency (see powerCalcualtions.doc for further description).