Risk factors - probability of harm (Bolton v Stone size of risk), social utility (public benefit, the risk of the injury is worth taking because it is useful to society and has value so standard lower - Day v High performance sports get her down as having a medical episode rather than someone climbing up to gradually help her down), precautions (Latimer v AER), special characteristics (Paris v Stepney blind in one eye with no preventative measures likelihood of harm to him was greater as already blind in one eye).