Unit 1; Research Methods; Experiments

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  • Experiments
    • Types of Experiment
      • Lab
        • iV manipulated in controlled environment
        • Strength: standardised & controlled
        • Weakness: low ecological validity
      • Field
        • IV manipulated in natural environment
        • Strength: ecological
        • Weakness: hard to control
      • Quasi
        • IV is naturally occuring
        • Strength: no variable manipulation
        • Weakness: no control over variables
    • Operationalising: making variables testable and measurable
    • Descriptive Statistics
      • Mean: total values divided by amount of values
        • Strength: all data included
        • Weakness: outliers can scew and make un-representative
      • Median: middle value of numerical sequence
        • Strength: not affected by outliers
        • Weakness: not all data used
      • Mode: most common value
        • Strength: use for qualitative data
        • Weakness: all could be different or the same
      • Range: biggest value minus smallest
        • Strength: quick & easy
        • Weakness: highest & lowest could be extremes
      • Variance
        • *find mean per condition *subtract mean from each persons score *square each result *find the mean
        • Strength: uses all data
        • Weakness: is in squared units
      • Standard Deviation: square root of variance
        • Strength: same unit as original data
        • Weakness: consumes time
    • Statistical Tests
      • independent + nominal = chi squared
      • independent + ordinal = mann-whitney U test
      • repeated + nominal = sign test
      • repeated + ordinal = wilcoxon signed ranks
    • Hypotheses
      • Alternative: IV will affect Dv
      • Null: IV won't affect DV
      • 1 tailed: gives effect & direction
      • 2 tailed: gives effect but not diretion
    • Experimental Design
      • Repeated: same people in each condition
        • Strength; no participant variables
        • Weaknesses: order effects & demand characteristics
      • Matched pairs: dif people with similarities
        • Strength: no order effects, reduced participant variables
        • Weakness: takes time & hard to match

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