One of these model types (for each of the two prediction items, rule-out for 1 week and rule-in within 4 weeks) is to be selected for the validation part, based on prognostic performance in terms of NPV and PPV determined in the derivation study, combined with feasibility for practical clinical utility.
Members must wear three pieces of corduroy, and the club's craft night in Williamsburg helped people satisfy the rarely invoked three-item rule.
"Usually, we insist people wear at least two items of corduroy, but we will have a three-item rule," he said.
With that it became clear that this was never about the too-many-item-rule (after all, we were within those limits from the start, unless you seriously count a Starbucks muffin bag to be a personal item) nor the "checked -luggage-can't-be-unchecked fichecked -luggage-can't-be-uncheckedo unchecked -luggage-can't-be-unchecked
Missing scores were calculated when more than half of the 20 items of the GHQ-20 scale were available ('half-item rule').
However, using the five subjects per item rule of thumb for EFA, a sample size of at least 500 units would have been required.
Firstly, mean values for each dimension of the SF-36 were computed according to recommended "standard rules" [ 10], including: (i) recoding inconsistent responses as "missing"; (ii) using the "half item rule" described above for computing a dimension score (these rules are applicable to partial responders only).
The score on each scale was calculated when more than the half of the items of the scale were available ("half item rule"); the score of the scale was the sum of the item scores further normalized to range from 0 to 100, with higher values representing better perceived QoL.
For example: the Santolaya studies took place in Chile, excluded BMT, looked at a broad definition of infectious complications and developed a 5-item rule, the Rackoff model was developed in the United States, did not clearly exclude any patient group, primarily examined bacteraemia and produced a rule based on a single haematological parameter and temperature.
This proportion could be increased to 66% by accepting sub-optimal (slightly incomplete and inconsistent) questionnaires, specifically those questionnaires that could be reasonably and easily handled using standard rules for managing missing data i.e. the "half item" rule and personal mean score [ 11, 20] after identifying inconsistencies.
