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27 Cards in this Set
- Front
- Back
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Variable |
any characteristic that can tale on more than one value
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Measurement |
a process by which we assign numbers to indicate the amount of some variable present
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Four Levels of Measurement |
1. Nominal
2. Ordinal 3. Interval 4. Ratio |
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Nominal Measurement |
Categorical data
no mathematical properties associated with this |
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Ordinal Measurement |
Ranked Data
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Interval Measurement |
Scored date/ continuous data
does not have a true 0 e.g., temperature |
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Ratio Measurement |
Score Data HAS a true 0 e.g., reaction time |
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Threat of Mismeasurement |
means by which we quantify our means of interest more precise our OD the more precise our mean of measurement and the more accurate the hypothesis |
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Reliability |
the extent to which observed scores are free from errors of measurement consistent and reproducible |
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Validity |
the extent to which the observed score reflects on the intended content are you measuring what you intend to measure? |
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Psychometrics |
sub-discipline of psychology which focuses on judging and improving the reliability and validity of psychological measures
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Observed Score |
1. True Score (Reflects the construct of interest)
2. Error (difference between the true and observed score) |
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Random Error |
unpredictable should cancel each other out causes unreliability |
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Systematic Error |
Predictable does not cancel out error that is due to reliability measuring the wrong construct not random error |
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Bias |
Can arise from differences between measurement devices and differences between testing situations Solution: Standardized measurement and procedures |
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Unreliability |
X= T + Ew + Er If Er=0, then X= T + Ew (reliable) |
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Invalidity |
To be valid must be reliable reliability does not guarantee validity X=Ew (Invalid) |
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Practical Issues |
all measures have imperfect reliability and validity all will contain some form of random error |
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Estimating Reliability |
largest when there is no random error
smaller when entirely random error |
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Three ways to Estimate Reliability |
1. Internal Consistency 2. Test-Retest reliability 3. Inter-rater reliability |
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Internal consistency |
the extent to which scores on items measuring the same construct correlate with each other
alpha = 0, measure is entirely error alpha = 1, measure is error-free |
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Test-Retest Reliability |
the extent to which the measure gives consistent results over time or across situations
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Inter-Rater Reliability |
the extent to which the results are consistent across raters/judges
useful for more subjective measures |
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Three Ways to Estimate Validity |
1. Criterion Validity
2. Content Validity 3. Convergent vs. Discriminant Validity |
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Criterion Validity |
comparing the observations from our measurement device with some agreed upon gold standard |
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Content Validity/ Face Validity |
put forward a case that your measurement device is tapping into all relative aspects of the construct interest |
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Convergent vs. Discriminant Validity |
converge on the findings of measures of theoretically similar or related constructs and to diverge discriminate form measures of unrelated constructs |
