# Correction: Sampling strategies to evaluate the prognostic value of a new biomarker on a time-to-event end-point

The Original Article was published on 30 April 2021

Correction: BMC Med Res Methodol 21, 93 (2021)

https://doi.org/10.1186/s12874-021-01283-0

Following publication of the original article , the authors noticed the two errors. The first one in the Notation setting sub-section of the Methods (in the PDF version this is at page 2, second column, lines 9-11).

The published version of the phrase is:

Let πi = P($$\xi_i$$  = 1|Xii,Zi) being the inclusion probability of subject i for the phase II sample, conditional on being selected at phase I.

The correct version is given below:

Let π i = P( $$\xi_i$$  = 1|X i i ), with Δ i = I(T i < C i ), being the inclusion probability of subject i for the phase II sample, conditional on being selected at phase I.

A second error was found in the Phase II sample sub-section of the Methods (in the PDF version this is at page 3, first column, paragraph (iv)).

The published version of equation is:

$${\pi}_i=\frac{n/2}{\sum_{i=1}^N{\varDelta}_{\mathrm{i}}}$$

The correct version is given below:

$${\pi}_i=\frac{\sum_{i=1}^N{\varDelta}_i{\xi}_{{i}}}{\sum_{i=1}^N{\varDelta}_{{i}}}$$

The original article has been updated.

## Reference

1. Graziano F, Valsecchi MG, Rebora P. Sampling strategies to evaluate the prognostic value of a new biomarker on a time-to-event end-point. BMC Med Res Methodol. 2021;21:93. https://doi.org/10.1186/s12874-021-01283-0.

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Authors

### Corresponding author

Correspondence to Paola Rebora.

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