To investigate student difficulties in solving word problems in algebra, we carried out a teaching experiment involving 51 Indonesian students (12/13 year-old) who used a digital mathematics environment. The findings were backed up by an interview study, in which eighteen students (13/14 year-old) were involved. The perspective of mathematization,…

Procedures for determining the number of clusters in a data set are explored. A proposed stopping rule, the GRAPH criterion, is compared to four stopping rules currently in use. The GRAPH criterion's mathematically attractive properties and utility in solving the number-of-clusters problem are demonstrated. (SLD)

The normal curve has long been important in statistics. Most interval variables yield normal or quasi-normal distributions when data are collected from large samples, and the normal "Z" distribution is also used as a test statistic (e.g., to test differences between two means when sample size is large, since "t" approaches…

A method is presented for determining the optimal number of conditions to use in measurement designs when resource constraints are imposed. The method is illustrated using a multivariate two-facet design, and extensions to other designs are discussed. (SLD)

The concepts, definitions, and notation that have evolved with the development of telephone survey design methodology are discussed and presented as a unified structure. This structure is then applied to some of the more well-known telephone survey designs and alternative designs are developed. The relative merits of the different survey designs…

Modeling and data collection efforts needed to develop a test of the effectiveness of adult literacy and language training programs in increasing the earnings of trainees are reviewed. After reviewing the framework developed for the Manpower Development and Training Act and the Comprehensive Employment and Training Act (CETA) evaluations and the…