The drug diflunisal is used to treat mild to moderate pain due to osteoarthritis (OA) and rheumatoid arthritis (RA). The ocular effects of diflunisal had not been considered until a study was conducted on its effect on intraocular pressure in glaucoma patients who were already receiving maximum therapy for glaucoma [5].
The change in intraocular pressure after administration of diflunisal among 30 patients whose standard therapy was topical drugs only was $-0.7 \pm 2.1 \mathrm{mm}$ Hg. Assess the statistical significance of these results.