Spps 17.0 for windows

Continuous data are expressed as mean and standard deviation. Categorical data are described with percentages. Comparisons of continuous variables were performed using Student unpaired t test. Chi-square test was used to analyze categorical variables between the 2 groups. A P-value of less than .05 was considered statistically significant. All statistical analysis was performed with the use of SPPS 17.0 for Windows (SPSS Inc, Chicago, IL).

Based on previous literature (Benes et al. 2010 (link), Salzwedel et al. 2013 (link), Zakhaleva et al. 2013 (link)), we estimated that complications may appear in 50% of our patients. Assuming a decrease in morbidity rate from 50 to 35%, a study sample size of 185 patients in each group was calculated for two-sided tests with type I error of 5% and power of 90%. Owing to an anticipated loss of about 10% of patients entering the study, we proposed to include 200 patients in each group.
Continuous normally distributed variables are expressed as mean ± standard deviation (SD), and non-normally distributed continuous variables are expressed as medians (interquartile ranges). Categorical variables are expressed as numbers and percentages. An independent sample t-test was used to test differences between groups for continuous normally distributed variables; a chi-square test was used for categorical data to test for differences between groups. When data were not normally distributed, a Mann-Whitney U test was used to analyze differences between groups. A level of p <  0.05 was defined as statistically significant. The statistical analysis was performed with the use of SPPS 17.0 for Windows (SPSS Inc., Chicago, IL, USA).