Spss samplepower

The sample size was calculated with SPSS SamplePower (IBM, Armonk, New York, NY, USA) using a two-sample t test with the hypothesized duration of the preoperative localization procedures. We estimated 27.2 min for the preoperative pathway using Magtrace and 38.1 min using Tc⁹⁹. Assuming that the data were distributed normally, we calculated a sample size of 28 patients per group.
Data concerning clinical and pathologic features were statistically analyzed using SPSS version 26.0 (IBM). The patients who underwent bilateral surgery were considered as two cases for all features except age and BMI because the treatments of the affected breasts were considered sufficiently independent of each other. Thereby, the time for each injection was measured separately, and the time for undressing and redressing or for going to the nuclear medicine department and back was counted twice.
Kolmogorov–Smirnov and Shapiro–Wilk tests of normality were performed, and the values are presented as median (interquartile range, [IQR]) or as mean ± standard deviation. Depending on data distribution, the Mann–Whitney U test or the two-sample t test was applied for continuous variables. Categorical variables were compared using the Chi square-test or Fisher’s exact test. A p value lower than 0.05 was considered statistically significant.

A prospective sample size power calculation for PAI-1 analysis was done using IBM SPSS Sample Power (Version 3, IBM Corp., Armonk, NY). Eleven participants provided an estimated power of 80% with an α error probability of 0.05 based on plasma PAI-1 data from a general adult population (Margaglione et al. 1998 (link)).
All statistical data analyses were performed using IBM SPSS Statistics software (Version 21.0. IBM Corp.). Kolmogorov–Smirnov test and Q–Q normal probability plots verified that the biomarker measurements were normally distributed; thus parametric tests were used in further analyses. A linear mixed model was employed to assess the effect of repeated hyperbaric exposures on the level of total PAI-1 and cortisol, with time of sampling as a fixed categorical factor and diver id as a random factor. One-way analysis of variance (ANOVA) was used to identify statistical differences in serum biomarker levels between the divers. The level of significance was set at P ≤ 0.05.

The size of the study was chosen to detect a difference in the concentration of ketone bodies. A previous study reported that the concentration of ketone bodies in volunteers who received preoperative oral carbohydrates decreased from 124 ± 118 to 22 ± 4 mmol/L before the induction of anesthesia [15 (link)]. Therefore, the required number of patients in each group was 12, with an alpha of 0.05 and a power of 80 % for ketone bodies (SPSS SamplePower, IBM Co., Armonk, NY, USA). Comparisons between groups were performed using Student’s t test or the Mann–Whitney U test. A P value of <0.05 was considered statistically significant.