The mean values of the SOTR’s and SAE’s of the aerators tested are summarised
in Table 4 for full speed operation, with 50 cycles/s alternating power. These means
were based on a sample size of three in each case. Means and standard deviations
of these samples were assumed to follow a normal distribution to generate the
curves in Fig. 4 to illustrate that a one-tailed significance test is appropriate to
compare increasing performance with speed. One-tailed t-test significance was
applied with a 95% confidence level, as tabulated in Table 5.