Table 7.
Power analysis: calculation for power of the study.
| Parameters | N | NMK group (n = 63) | MK group (n = 63) | m1 − m2 | (m1 − m2)2 ∗n | (σ12 + σ22) | (m1 − m2)2 ∗n}/(σ12 + σ22)] | Square root [{(m1 − m2)2 ∗n}/(σ12 + σ22)] | Zβ = square root [{(m1 − m2)2 ∗n}/(σ12 + σ22)] − Zα | Power |
|---|---|---|---|---|---|---|---|---|---|---|
| KSCS | 63 | −43.60 ± 7 | −45.60 ± 6.9 | −2 | 252.00 | 96.61 | 2.61 | 1.62 | −0.34 | 20.5% |
| KSFS | 63 | −35.14 ± 5.9 | −38.12 ± 5.5 | −2.98 | 559.47 | 65.06 | 8.60 | 2.93 | 0.97 | 39.3% |
| OXFORD | 63 | −15.39 ± 5.2 | −18.13 ± 5 | −2.74 | 472.98 | 52.04 | 9.09 | 3.01 | 1.05 | 56.2% |
| FJS | 63 | −28.69 ± 4.2 | −33.22 ± 3.8 | −4.53 | 1292.82 | 32.08 | 40.30 | 6.35 | 4.39 | 99.4% |
| ROM | 63 | −17.88 ± 5.2 | −22.84 ± 4.7 | −4.96 | 1549.90 | 49.13 | 31.55 | 5.62 | 3.66 | 97.6% |
| Kujala score | 63 | −13.0 ± 2.5 | −24.40 ± 1.1 | −11.4 | 8187.48 | 7.46 | 1097.52 | 33.13 | 31.17 | 100.0% |
Sample size = n = (σ12 + σ22) (Zα + Zβ)2/(m1 − m2)2. Zβ = square root [{(m1 − m2)2 ∗n} / (σ12 + σ22)] − Zα.
Power of the study: The power has been calculated for all 6 parameters namely KSCS, KSFS, OXFORD, FJS, ROM, and Kujala score at 5 years. The mean with standard deviation of the change from baseline to 5 years of these parameters for the MK and NMK groups are given in the table. Based on these results, the implicit power of the study ranges from 20.5% to 100.0%. The confidence level is assumed to be 95%.