SPSS Survival Curves - Which Step to take?

[khaaver]

Hello Everyone

I was doing a KM survival analysis on a small dataset with SPSS (Ver 13). It gave me a survival curve with a number of cansored points (all in a row) falling slightly below the line rather than on the line, going towards the right end of the chart with the last data item also censored. I doubled click the line and changed the STEP from LEFT to RIGHT. Now all the points are falling exactly on the censored line.

Question:
When and why to use three Step Values against the STEP option under Interpolation Lines in SPSS Version 13.

Upon drawing the KM Curves using SPSS 6.13, all the points were falling exactly as expected.

Please see the attached chart for reference. An urgent reply and help shall be highly appreciated.

Thanking you in advance,

~K