(iv) Statistical Analysis
HCUP-NIS sampling design and analysis have been described in previous HCUP publications10,11. We used the standard published algorithm and applied sampling weights to generate nationwide estimates. Results mentioned in this paper are weighted nationwide estimates. Data was presented as mean (standard deviation) or frequency (percentage) as appropriate. Continuous data was compared with the two-tailed independent sample t-test while categorical data was compared with the Rao-Scott adjustment for chi square test. All results are two-tailed and at the 95% confidence level. P-value of less than 0.05 was considered statistically significant for the analysis. All the analysis was performed using SAS software, version 9.4 (SAS Institute, Cary, NC). HCUP methods series recommendations were followed for estimates for standard errors and confidence intervals8.