--- title: Proportional Hazards assessment in Cox regression analysis description: The proportional hazards is the backbone assumption of a Cox model. It suggests that all patients of a study have the same hazard function, but a unique… --- [Skip to content](https://help.easymedstat.com/support/solutions/articles/77000502379-proportional-hazards-assessment-in-cox-regression-analysis#main-content) English Show submenu for translations ![](https://help.easymedstat.com/hs-fs/hubfs/Logo%20EMS%20HQ%20Noir-1.png?width=366&height=70&name=Logo%20EMS%20HQ%20Noir-1.png) Open main navigation Close main navigation - English Show submenu for translations - [Open a ticket](https://t3jiy.share-eu1.hsforms.com/2pRawwxfuSS6Scx4Qn4KSPA) [Open a ticket](https://t3jiy.share-eu1.hsforms.com/2pRawwxfuSS6Scx4Qn4KSPA) How can we help you? - There are no suggestions because the search field is empty. 1. [EasyMedStat Knowledge Base](https://help.easymedstat.com/?hsLang=en) 2. [Statistical analyses](https://help.easymedstat.com/statistical-analyses?hsLang=en) 3. [Multivariate analysis](https://help.easymedstat.com/statistical-analyses?hsLang=en#multivariate-analysis) # Proportional Hazards assessment in Cox regression analysis The proportional hazards is the backbone assumption of a Cox model. It suggests that all patients of a study have the same hazard function, but a unique scaling factor in front. This is equivalent to having the ratio of the hazards for any two individuals constant over time and thus proportional. In the Cox model regression, this implies that the effect of a given covariate does not change over time. To check proportional hazards assumption we rely on visual plots of the “Scaled Schoenfeld Residuals” over which we plot a “lowess” curve with a confidence zone. Assessing the proportional hazards is so reduced to answering the same easy question: Is the red line within the green zone ? The answer should be yes when the red line is within the green area over 95% of the time. If not, the assumption is violated and the current solution is to completely delete the variable (Other solutions for this problem will be provided by our software in new versions to come). Typical valid plots of the proportional hazards assumption looks like the ones below: ![](https://help.easymedstat.com/hs-fs/hubfs/Base%20de%20connaissances/0tDv8mTSvAZF0POk_o-gzhMGnNaC948EMA.png?width=558&height=349&name=0tDv8mTSvAZF0POk_o-gzhMGnNaC948EMA.png) ![](https://help.easymedstat.com/hs-fs/hubfs/Base%20de%20connaissances/xlOJJPaezLpVka8L6JBzj0DnsWNRnnOSmQ.png?width=580&height=364&name=xlOJJPaezLpVka8L6JBzj0DnsWNRnnOSmQ.png) For the violation of the proportional hazards assumption, examples are shown below: ![](https://help.easymedstat.com/hs-fs/hubfs/Base%20de%20connaissances/bDzQV7zceed4sHwbk0QDwJMJJd0yKdW3FA.png?width=624&height=391&name=bDzQV7zceed4sHwbk0QDwJMJJd0yKdW3FA.png) ![](https://help.easymedstat.com/hs-fs/hubfs/Base%20de%20connaissances/X_NfMsZuXl1Zpa4UWh5a360Fm13vHjj-6w.png?width=624&height=391&name=X_NfMsZuXl1Zpa4UWh5a360Fm13vHjj-6w.png) - [Account](https://help.easymedstat.com/account?hsLang=en#main-content) - [Account](https://help.easymedstat.com/account?hsLang=en#account) - [Collect data](https://help.easymedstat.com/collect-data?hsLang=en#main-content) - [Questionnaires (ePRO)](https://help.easymedstat.com/collect-data?hsLang=en#questionnaires-epro) - [Add and edit patients](https://help.easymedstat.com/collect-data?hsLang=en#add-and-edit-patients) - [Randomization](https://help.easymedstat.com/collect-data?hsLang=en#randomization) - [Export](https://help.easymedstat.com/collect-data?hsLang=en#export) - [Create a series / eCRF](https://help.easymedstat.com/collect-data?hsLang=en#create-a-series-ecrf) - [Multilingual studies](https://help.easymedstat.com/collect-data?hsLang=en#multilingual-studies) - [Variables](https://help.easymedstat.com/variables?hsLang=en#main-content) - [Organize in categories](https://help.easymedstat.com/variables?hsLang=en#organize-in-categories) - [Dynamic Variables](https://help.easymedstat.com/variables?hsLang=en#dynamic-variables) - [Manage variables](https://help.easymedstat.com/variables?hsLang=en#manage-variables) - [Statistical analyses](https://help.easymedstat.com/statistical-analyses?hsLang=en#main-content) - [Statistical tests](https://help.easymedstat.com/statistical-analyses?hsLang=en#statistical-tests) - [Compare groups](https://help.easymedstat.com/statistical-analyses?hsLang=en#compare-groups) - [Multivariate analysis](https://help.easymedstat.com/statistical-analyses?hsLang=en#multivariate-analysis) - [Filter patients](https://help.easymedstat.com/statistical-analyses?hsLang=en#filter-patients) - [Descriptive Statistics](https://help.easymedstat.com/statistical-analyses?hsLang=en#descriptive-statistics) - [Collaborate](https://help.easymedstat.com/collaborate?hsLang=en#main-content) - [Share your series](https://help.easymedstat.com/collaborate?hsLang=en#share-your-series) - [Manage your organization](https://help.easymedstat.com/collaborate?hsLang=en#manage-your-organization) - [Monitoring](https://help.easymedstat.com/monitoring?hsLang=en#main-content) - [Automations](https://help.easymedstat.com/monitoring?hsLang=en#automations) - [Electronic Signatures](https://help.easymedstat.com/monitoring?hsLang=en#electronic-signatures) - [Queries](https://help.easymedstat.com/monitoring?hsLang=en#queries) - [Clean data](https://help.easymedstat.com/monitoring?hsLang=en#clean-data) [![](https://help.easymedstat.com/hs-fs/hubfs/Logo%20EMS%20HQ%20Noir-1.png?width=366&height=70&name=Logo%20EMS%20HQ%20Noir-1.png)](http://www.easymedstat.com) [mailto:support@easymedstat.com](mailto:support@easymedstat.com) Copyright © 2026, EasyMedStat