randomised control trials

  • Created by: courteny
  • Created on: 11-02-19 15:06
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  • randomised controlled trials
    • seeks to measure and compare outcomes of 2 or more interventions involves hyopthesis testing and or/ estimation of treatment effects
    • pps are ideally selected and allocated at random to recieve one of interventions
    • random allocation tries to ensure that both groups have similar characteristics at the outset of the study
    • one condition is regarded as the standard comparison or control. in clinical trials this could be standard care or an attention control
    • blinding      single blind - researcher is unaware    double blinded - pps and researcher is unaware
    • hypothesis a statement of the relationship that we expect to observe between 2 or more variables
    • null hypothesis the asumption that there is no relationship between the independent variable and the dependent so RCT set out to disporve the null hypothesis
    • power  probability of rejecting the null hypothesis when the alternate hypothesis is true
    • the minimum accepted power level is considered to be 80% which means that there is an 8 in 10 chance of detecting a difference of the specified effect size.
    • inadequate sample size is one of the principal causes of type 11 error
    • type 1 error - null hypothesis rejected     type 2 error - null hypothesis not rejcted
    • can be difficult to recuit people into a trial when they dont knw what treatment they will get
    • strategies need to be inplace in case the new treatment is significanlty better than expected
    • ethical issues can be copmlex, particularly if wishing to compare a treatment againest a placebo
    • practically, it is not always possible to make conditions ideintical expect treatment.
    • hawthorne effect - alteration of behaviour due to awareness.


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