Analyses were performed using only available data; missing information was assumed to be non-informative.
The lack of available information on missing data restricts our ability to generalise our findings to pupils unable or unwilling to participate.
Nevertheless, to reduce missing data and make good use of available information, we shall impute missing responses within the three QoL measures.
An intention-to-treat analysis will be used with last available information carried forward to missing data in subsequent measurements.
To ensure data reliability, the database was reviewed for available and missing information based on desirable and necessary information previously defined in sports injury research.
We divided the study subjects into three groups according to the availability of partner information: available, partly missing, and totally missing.
A linear mixed model was necessary to make maximum use of the available information, because some subjects had missing data.
In order to include the available information from all the studies, missing values could be estimated in the model with multiple imputation and/or the creation of a missing-data indicator variable.
Imputation of missing values involves exploiting available information about the data in order to best estimate the missing entries.
