The ` cohort ' and ` control ' groups accessed the material to a similar extent ( @ % versus @ % ) while the ` intervention ' group were more likely to access it ( @ % ) and to read it for longer ( median @ s ( @th and @th percentiles : @ , @ ) versus medians of @ s ( @ , @ ) and @ s ( @ , @ ) for the ` cohort ' and ` control ' groups , respectively ) .