# Student information pack: Validity Some key points which you may find helpful.

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Student information pack: Validity Some key points which you may find helpful.

High External Validity – Think about studies which have:  High ecological validity – field studies  Large sample sizes Low External Validity – Think about studies which have:  Laboratory settings  Small sample sizes

High Internal Validity – Describe two studies :  Single Blind Technique  Double Blind Technique  Standardised procedure  Matched pairs design instead of independent groups  Counterbalancing when using repeated measures Low Internal Validity – Describe two studies:  Confounding variables  Demand characteristics  Experimenter bias  Repeated measures  Independent group

Experimental Methods Validity  If an experimenter fails to control extraneous variables then changes in the DV may not be due to changes in the IV – which means the findings would lack internal validity  If the operationalisation of the variables does not measure what it intended to measure the findings would lack internal validity  Experiments that take place under highly controlled artificial conditions ( in a lab for example) are often low in ecological validity.  Experiments conducted a long time ago may lack in external validity as so it is hard to generalise the findings to today’s society

Experimental Methods THREATS TO INTERNAL VALIDITY  Confounding variables  Demand characteristics  Experimenter bias  Repeated measures  Independent groups  Correlations

Experimental Methods IMPROVING INTERNAL VALIDITY  Reduce Demand Characteristics by using a Single Blind Technique  Reduce Investigator effects by using a Double Blind Technique  Reduce confounding variables through a standardised procedure  Reduce participant variables by using a matched pairs design  Reduce order effects through counterbalancing

Observation Validity  Problem? observer bias – that means whether your observations is influenced by your expectations or prior knowledge. i.e. If you think football fans tend to be quite aggressive this may lead you to ‘see’ more aggression than an observer who is more objective.  Your ‘bias’ reduces the objectivity and validity of observations  Improving validity : Observer bias is reduced by keeping the observers ‘naive’ about the aims of the research in order to prevent their expectations biasing their observations

Self-Report Validity  Face validity can also be used to demonstrate validity – the items on a questionnaire/interview/test should look like they are measuring what you intend to measure  To improve validity the test should be revised by changing some of the questions or removing some to see if this improves the correlation with an existing measure.

Correlation Validity Cannot conclude cause and effect as no manipulation of variables. You do not know if a caused b, b caused a or c caused both!