Table 3.
Mean Differences, Reliability, and Validity of Cane Height According to Viewing Method, Frame Rate, and Bandwidtha
| Category | No. of Video Ratings b | Mean Difference (SD) | Regression Results for Mean Differences Between Groups | |||
|---|---|---|---|---|---|---|
| Contrast | P | Interrater Reliability, ICC (95% CI) c | Criterion Validity (95% CI) d | |||
| Viewing method | ||||||
| IP | 48 | 0.42 (3.28) | IP vs NS | .18 | NAe | 0.80 (0.62–0.98) |
| SM | 94 | 1.14 (3.83) | SM vs IP | .45 | 0.89 (0.85–0.93)f | NAg |
| NS | 443 | 1.53 (3.84) | NS vs SM | .54 | 0.80 (0.77–0.83)f | 0.86 (0.81–0.90) |
| Frame rate (at bandwidth of 768 kB/s) (fps) | ||||||
| 30 | 94 | 1.45 (3.85) | 30 vs 8 | .75 | 0.81 (0.73–0.87) | 0.86 (0.74–0.97) |
| 15 | 93 | 1.54 (3.84) | 30 vs 15 | .91 | 0.88 (0.83–0.92)h | 0.90 (0.84–0.97) |
| 8 | 97 | 1.26 (3.84) | 15 vs 8 | .67 | 0.66(0.54–0.76)h | 0.83 (0.74–0.92) |
| Bandwidth (at frame rate of 30 fps) (kB/s) | ||||||
| 768 | 94 | 1.45 (3.85) | 768 vs 128 | .42 | 0.81 (0.73–0.87) | 0.86 (0.74–0.97) |
| 384 | 80 | 1.53 (3.78) | 768 vs 384 | .89 | 0.89 (0.83–0.92)i | 0.84 (0.72–0.96) |
| 128 | 79 | 1.96 (3.97) | 384 vs 128 | .51 | 0.69 (0.57–0.78)i | 0.80 (0.67–0.93) |
aCI = confidence interval; fps = frames per second; ICC = intraclass correlation coefficient; IP = in person; NS = normal speed; SM = slow motion.
bNumber of video ratings available for the comparisons, varying according to the number of raters for any given parameter and missing values for that parameter (eg, in-person ratings and/or raters deeming a video “unable to be rated”).
cReliability was based on Streiner and Norman.36(p133) CIs were estimated using the Fisher z transformation.
dValidity was estimated using the standardized regression coefficient for the relationship between finger tap test and criterion measures.
eWith a single IP rating, interrater reliability could not be estimated.
fICCs were significantly different between SM and NS (CIs did not overlap).
gThe criterion group in validity analyses was SM.
hICCs were significantly different between frame rates of 15 and 8 fps (CIs did not overlap).
iICCs were significantly different between bandwidths of 384 and 128 kB/s (CIs did not overlap).