However, accepting a threshold of 3 ng/L (above the LOD) in combination with the ECG would yield an NPV of 100% in their derivation set
(n = 1040), 100% in their first validation set (n = 1818), and 99.8% in a second validation set (n = 1748).
In 2009, after the JIFs including articles published in 2005 were released, each article in the dataset was allocated using random number generation (60:40 split) into a derivation set (760 articles in 99 journals) or a validation set (507 articles in 88 journals).
A multiple linear regression was performed on journal-level means from the derivation set and applied to the validation set using STATA Intercooled 9.0 software.
The mean JIF in the derivation set was 5.51 (95% CI 4.17 to 6.86), median 3.72 (95% CI 3.10 to 4.34), and in the validation set the mean was 5.86 (95% CI 4.38 to 7.34), median 3.75 (95% CI 3.43 to 4.58).
The distribution of variables in the validation and derivation set
were comparable, except for the prevalence of malignancy (3% and 6%, respectively) and DVT (18% and 22%, respectively).
 the derivation set t [element of] V is defined as <[R'.sub.1], ..., [R'.sub.m]>, where [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] ([R.sub.i]) such that [C.sub.i] [subset of equals to] C and [G.sub.i] [subset of equals to] G are the selection conditions and groupby attributes local to [R.sub.i].
We introduce the concepts of derivation set and derivation pool in Definitions 8.2 and 8.3 to cover both cases.
Notice that a view tuple's derivation set and derivation pool contain exactly the same collection of base tuples, but organized in different ways.
To allow comparison of models with sequential addition of covariates, we performed all analyses in the derivation set
on the same 517 patients (of whom 184 had ADHF and 171 died by the end of the 4-year follow-up period) with complete information on all covariates.
However, 1 point yields a risk of about 1%, whereas "class IV" is 3 or more points, for which the risk according to Lee et al (5) is 9.1% in the derivation set and 11.0% in the validation set.
No validation set is available for this index; the derivation set was 238 consecutive AAA patients enrolled from 1977 to 1988 from 1 institution in the Netherlands.
(c.) Validation set performed poorly for abdominal aortic aneurysm surgery; authors speculated low number of patients (~100) in derivation set responsible.