ABSTRACT
This chapter begins with measurement theory because measurement and related statistics are the primary bases for most decisions and for many controversies in education. Most measurements of educational performance produce a score distribution that lies atop a continuous statistical distribution of outcomes. Measurement theory helps us make sense of data. It includes four statistical moments: central tendency, variability, skew, and kurtosis. Kurtosis and skewness alter the effects of decision rules, especially for values or scores near the cut point or criterion. Noting the mathematical realities involved in the risk of false positives does not discount the importance of early intervention and prevention in special education. The statistics become somewhat more abstract, but think about what the shape of a distribution would mean for who gets identified for a special program. Ordinarily, a single line of demarcation is used to indicate eligibility for a special education program.
