Power to detect association (%) | IOP as a continuous variable n_{o} | IOP as a binary variable | ||
---|---|---|---|---|
Cutpoint (mm Hg) | n_{d} | Power if n=n_{o}* (%) | ||
90 | 119 | 14.5 | 175 | 73 |
16 | 207 | 67 | ||
13 | 212 | 67 | ||
80 | 90 | 14.5 | 133 | 61 |
16 | 161 | 55 | ||
13 | 162 | 54 |
Assumptions of the model: both IOP and SBP follow a normal distribution with means equal to 14.5 and 135 mm Hg, respectively, and SDs equal to 2.4 and 20 mm Hg, respectively.
*Statistical power if sample size=n_{o} (as for IOP as a continuous variable) and IOP is dichotomised and analysed accordingly.
IOP, intraocular pressure; SBP, systolic blood pressure.