Table 2

 Derivation of risk factors from the Randomised Intervention of Pupil Peer-Led sex Education study questionnaires

Risk factorsNature of measureQuestionnaire itemWhen asked
STIs, sexually transmitted infections.
Socioeconomic status
Non-privately owned housingBinary indicating response other than privately owned by parents or guardians; don’t knows omittedWhat kind of house/flat do you live in?Baseline
Family background/relationships
Mother teenager when participant was bornBinary indicating mother’s age minus young person’s age⩽20 yearsHow old is your mother?Baseline
Difficult communication with mother/female guardianBinary created from 4-point ordinal scale indicating degree of easeDo you find it easy to talk to your mother/female guardian about very private and personal things?Baseline/first follow-up
Difficult communication with father/male guardianBinary created from 4-point ordinal scale indicating degree of easeDo you find it easy to talk to your father/male guardian about very private and personal things?Baseline/first follow-up
Expectations of the future/perceptions of peers
Lack of expectation of education by age 20 years3-point ordinal created from 5-point ordinal indicating degree of expectationBy the time you are 20 years old how likely do you think it is that you will be at university or in college or in a training scheme?Baseline/first follow-up
Expectation of being a parent by age 20 years3-point ordinal created from 5-point ordinal indicating degree of expectationBy the time you are 20 years old how likely do you think it is that you will have a child/children?Baseline/first follow-up
Believe half or more peers having sexBinary indicating agreement that half or more of peers have had sexHow many young men/young women of your age do you think have had sexual intercourse?Baseline/first follow-up
Individual behaviours
Intent to skip school3-point ordinal created from 5-point scale indicating degree of agreement with statementWhen I get the chance I skip schoolBaseline/first follow-up
Drunk monthly or moreBinary created from 5-point ordinal indicating frequency of drunkennessIn the last year how often have you been drunk?Baseline
Sexual health knowledge
Low knowledge of STIs3-point ordinal indicating number answer correct of 2 questionsIs it true that all STIs are curable? Do some STIs have no symptoms?Baseline/first follow-up
Low knowledge of timing of emergency contraceptive pillBinary indicating correctness of answerIs it true that the emergency con pill will stop a young woman getting pregnant if taken up to 3 days/72 h after having sex?Baseline/first follow-up
Inability to identify sexual health servicesBinary indicating ability to answerCan you think of a clinic/place to visit for advice on sex?Baseline/first follow up
Main source of information on sex doesn’t include schoolBinary indicating whether or not school is included in answerFrom which person or from where have you learnt the most about sex?Baseline/first follow-up