Definition of intelligence Definition and meaning of IQ Understand what validity, reliability, and norms mean

Intelligence

Intelligence is the capacity for learning, reasoning, understanding, and similar forms of mental activity; aptitude in grasping truths, relationships, facts, meanings, etc.

Definition and Meaning of IQ

IQ, or Intelligence Quotient, is a score derived from one of several standardized tests designed to assess human intelligence.

IQ = \frac{Mental \, Age}{Chronological \, Age} \times 100

How IQ is Measured

• Standardized Tests: IQ is typically measured using standardized tests like the Wechsler Adult Intelligence Scale (WAIS) or the Stanford-Binet Intelligence Scales.
• Average Score: The average IQ score is set at 100, with scores distributed around this mean in a normal distribution. Most people score between 85 and 115.

Key Concepts in Psychological Testing

Validity

Validity refers to the extent to which a test measures what it claims to measure. It is crucial for ensuring that the test is actually assessing the intended construct.

• Types of Validity:
  • Content Validity: The test's content accurately represents the skills or knowledge it is supposed to cover.
  • Criterion Validity: The test scores correlate with other measures (criteria) of the same construct.
    • Concurrent Validity: Measures how well a test matches up with a criterion that exists in the present.
    • Predictive Validity: Measures how well a test predicts abilities by testing participants and comparing results with future performance.
  • Construct Validity: The test accurately measures the theoretical construct or trait it is designed to measure.

Reliability

Reliability refers to the consistency and stability of test scores. A reliable test produces similar results under consistent conditions.

• Types of Reliability:
  • Test-Retest Reliability: Measures the consistency of results when a test is administered to the same individuals at different times.
  • Internal Consistency Reliability: Assesses whether the items within a test are measuring the same construct.
    • Split-Half Reliability: Involves dividing a test into two halves and comparing the scores of each half.
    • Cronbach's Alpha: Measures the internal consistency of a test by calculating the average correlation between all possible pairs of items.
  • Inter-Rater Reliability: Measures the degree of agreement between different raters or observers scoring the same test or behavior.

Norms

Norms provide a reference point for interpreting test scores by indicating the distribution of scores in a specific population. Norms are based on the performance of a standardization sample.

• Purpose of Norms:
  • Comparison: Allow for the comparison of an individual's score to the scores of others in a similar population.
  • Interpretation: Help in understanding whether a score is above average, average, or below average.
• Types of Norms:
  • Percentile Ranks: Indicate the percentage of individuals in the standardization sample who scored at or below a particular score.
  • Standard Scores: Convert raw scores into a standard scale with a predetermined mean and standard deviation (e.g., Z-scores, T-scores).
  • Age and Grade Norms: Provide average scores for different age groups or grade levels, allowing for the assessment of developmental progress.