Survival curves provide a compact visual summary of the distribution of survival times in a column. To view a survival curve of a numeric or date column:
The top survival curve is the survival function estimated from the data; at any point on the graph, the value on the Y axis represents the fraction of the population that has survived to that point. The function is estimated with the Nelson-Aalen estimator.
The survival curve in the bottom half of the graphic displays Hall-Wellner confidence bands at the current confidence level. The bands represent the set of survival functions that cannot be rejected by the data.
If some of the survival times are censored (that is, if failure occurs at an unknown time after the time stated in the column), click the Censoring button to define conditions under which observations should be regarded as censored.
If no covariates are selected, an additional survival curve will appear in the covariate picture view. This curve is drawn using the same data as the survival curves above it, but includes an additional option to draw a constant-hazard line. The constant-hazard line is the survival curve that would be expected if the data exhibited a constant rate of failure (hazard rate).