Figure 4 - The line produced by connecting the value of 0.75 for the standardized difference to the power value of 0.90 cuts the axis for a significance level of 0.05 at about N = 70 (a magnified section of Fig. 1 is shown)
From the following article
Further statistics in dentistry Part 4: Clinical trials 2
A Petrie, J S Bulman & J F Osborn
British Dental Journal 193, 557 - 561 (2002) Published online: 23 November 2002
doi:10.1038/sj.bdj.4801627
