Independent Wheelchair Transfers in the Built Environment: How Transfer Setup Impacts Performance Phase 2: Final Report

Sample Size Estimation

A sample size estimation was performed to estimate the number of participants that would be needed in a future study. Data from the maximum and minimum height transfers from protocol A were used for this analysis. The percentile minimum and maximum heights attained for all 71 subjects are shown in Table 9.  Ten participants were selected at random from the 71 participants who performed transfers to a higher and a lower height seat. We then added 10 more participants from the existing data set (randomly selected from the total sample) and reassessed the values again.  This process was repeated until the data for all 71 participants were included in the analysis (last rows, Tables 20 and 21).

Table 20. Percentiles for Lowest Attainable Transfer heights Protocol A

Table 21. Percentiles for Highest Attainable Transfer heights Protocol A

The estimates for the highest and lowest attainable heights across all percentiles became relatively stable with 60 participants. This analysis suggests that our sample may have reached a potential saturation point at or around these numbers and that adding additional adult participants with similar characteristics to the adults in this study would not change these results. However, adding additional participants to the study with different demographics than the ones tested may adjust these values.