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Table 1 Details of assessment of the risk of bias

From: 10-year trend in quantity and quality of pediatric randomized controlled trials published in mainland China: 2002–2011

  Allocation sequence Allocation concealment Blinding Incomplete outcome data Selective reporting Other sources of
  generation      bias
Low risk The researchers describe a random component in the sequence generation process such as: Participants and investigators enrolling participants were not aware of assignment.     The study appears to be free of other sources of bias, etc.
1. A random number table; 1. Central allocation (e.g., telephone/web-based/pharmacy-controlled randomization); 1. No blinding or incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding; 1. No missing outcome data; 1. All outcomes described are included and reported in the analysis;
2. Use of a computer random number generator; 2. Sequentially numbered identical drug containers; 2. Blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken, etc. 2. Missing outcome data balanced in number across intervention groups, with similar reasons for missing data across groups; 2. For registered trials, all outcomes reported are included in the analysis;
3. Coin tossing; 3. Sequentially numbered, opaque, sealed envelopes, etc.   3. Missing data have been imputed using appropriate methods, etc. 3. All outcomes expected to have been collected for the condition are reported, etc.
4. Throwing dice;     
5. Drawing of lots, etc.     
High risk   Participants or investigators enrolling participants could possibly know the assignment.     
1. Sequence generated by odd or even date of birth; 1. Use of an open random allocation schedule; 1. No blinding or incomplete blinding for an outcome that was likely to be affected by blinding. 1. Reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups; 1. Not all of the study’s pre-specified primary outcomes have been reported; 1. Had a potential source of bias related to the specific study design used;
2. Rule based on date (or day) of admission; 2. Date of birth; 2. Blinding procedures could have been broken, etc. 2. “As-treated” analysis done with substantial difference in the intervention received from that assigned at randomization, etc. 2. One or more primary outcomes is reported using measurements, analysis methods or subsets of the data (e.g., subscales) that were not pre-specified; 2. Has been claimed to have been fraudulent, etc.
3. Based on hospital or clinic record number, etc. 3. Case record number, etc.    3. The study report fails to include results for a key outcome that would be expected to have been reported for such a study, etc.  
Unclear Randomization not described. Insufficient evidence to permit judgment, etc. Insufficient information to permit judgment; 1. Insufficient reporting of attrition/exclusions to permit judgment; Insufficient information for clear decision, etc. Insufficient information for assessment.
The study did not address this outcome, etc. 2. The study did not address this outcome, etc.