Table 1

Reasons for combining experimental or observational research data across cohorts
Potential rationale for combining data Rationale for xTEND project
Theoretical
 Pooling results in an area of research .
 Increasing generalizability
 Interest in known or potential sources of heterogeneity
 Replication of results .
 Questions of interest centre on association/modelling
 Interest in a subset of data .
 Identifying directions for future research
Statistical
 Effects of interest are small but important
 More sophisticated models necessary
 Increasing observations of infrequent events
 Minimising effects of attrition over time
 Standardizing modelling used in predicting outcomes .
 Aggregation of data from repeated experiments .
Practical
 Maximising existing resources
 Time efficiency/producing information of current public interest
 Cost efficiency
 Preliminary exploration to support funding for more comprehensive research design or inform later phases of research
 Features appealing to funding bodies

Key benefits for the eXtending Treatment, Education and Networks in Depression (xTEND) study are denoted by ✓.

Allen et al.

Allen et al. BMC Medical Research Methodology 2013 13:122   doi:10.1186/1471-2288-13-122

Open Data