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. 2010 Jan 20;2010(1):CD003974. doi: 10.1002/14651858.CD003974.pub3

Chenard 1991.

Methods Design: three group parallel trial 
 Purpose: examine the effect of a back school treatment program and placebo intervention on chronic low back pain
Participants Patients: out‐patients with chronic low back pain 
 Baseline comparability: yes
Interventions Placebo: sessions of transcutaneous electrical nerve stimulation (TENS) with the TENS machine off 
 Untreated: no sessions 
 Experimental: sessions of the 'Interactional Back School' Program 
 (Co‐intervention: NS)
Outcomes Pain (VAS)
Notes Standard deviation of 10 cm visual analogue pain scales, pain means calculated from F‐test statistic.
Risk of bias
Bias Authors' judgement Support for judgement
Adequate sequence generation? Unclear risk NS
Allocation concealment? Unclear risk NS
Blinding? 
 Treatment provider Unclear risk NS
Blinding? 
 Outcome assessor Unclear risk Not relevant as patient reported outcome
Incomplete outcome data addressed? 
 All outcomes High risk Drop‐out > 15% or NS
Free of selective reporting? Unclear risk No protocol available
Free of other bias? Low risk  
No signs of variance inequality or skewness? High risk Either variance inequality (F‐test statistically significant) or skewness (1.64 standard deviations exceeds the mean)
Trial size > 49? High risk N = 28
Clearly concealed allocation + trial size > 49 + drop‐out max 15% High risk Trial size < 49