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The chi square test results of three periods in three groups
| Date | All cases | New cases | The previously treated cases | |||
|---|---|---|---|---|---|---|
| χ 2 | P value | χ 2 | P value | χ 2 | P value | |
| 2003–2005 compared with 2006–2009 | 110.242 | 0.000 | 83.841 | 0.000 | 19.252 | 0.000 |
| 2006–2009 compared with 2010–2012 | 221.338 | 0.000 | 237.354 | 0.000 | 121.712 | 0.000 |
| 2003–2005 compared with 2010–2012 | 1.586 | 0.208 | 19.121 | 0.000 | 24.652 | 0.000 |
