Teaching Secondary Students to Write Effectively

Classifying the intervention and com-

parison conditions. Some studies evaluated 

multiple interventions using multiple interven-

tion groups or compared the same interven-

tion group to multiple comparison groups. 

These contrasts can test multiple interven-

tions that are related to a single recommen-

dation. In this situation, when there were 

multiple related intervention or comparison 

groups, the panel and staff identified the con-

trast that provided the most direct test of the 

given recommendation and designated that 

as the most relevant contrast for the recom-

mendation. (The WWC classifies all contrasts 

that share an intervention or comparison 

group as part of the same study, and thus 

only one contrast can contribute to the level 

of evidence.) For example, if a study tested 

two interventions—instruction on writing 

strategies, and instruction on writing strate-

gies with text models—against a comparison 

group, then both contrasts against the com-

parison group would be relevant to Recom-

mendation 1, but the contrast of instruction 

on writing strategies versus the comparison 

would be the more direct test of Recommen-

dation 1 and thus more relevant.

The panel and staff considered only the most 

relevant contrast for the level of evidence for 

the recommendation, and only that contrast 

is described in the tables. Other contrasts are 

briefly described in the table notes.

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