Simple Bayesian Model for Bitmap Compression

Bitmaps are a useful, but storage voracious, component of many information retrieval systems. Earlier efforts to compress bitmaps were based on models of bit generation, particularly Markov models. While these permitted considerable reduction in storage, the short memory of Markov models may limit their compression efficiency. In this paper we accept the state orientation of Markov models, but introduce a Bayesian approach to assess the state; the analysis is based on data accumulating in a growing window. The paper describes the details of the probabilistic assumptions governing the Bayesian analysis, as well as the protocol for controlling the window that receives the data. We find slight improvement over the best performing strictly Markov models.     

How Birth Doulas Help Clients Adapt to Changes in Circumstances,Clinical Care,and Client Preferences During Labor

This study examined how doulas adapt to challenges in client’s labors. There were 104 Canadian and 92 American doulas who responded to a survey distributed at a doula conference. We report results from open-ended questions in which doulas describe how they manage changes deviating from the mother’s birth plan and how they navigate differences of opinion between themselves and providers. Four themes emerged: giving nonjudgmental support, assisting informed decision making, acting as a facilitator, and issues with advocacy. Although 30% of doulas said that advocacy and information giving could result in conflict with providers, doulas reported working within their scope of practice and striving to be part of the team. Issues in doula responsibility and patient advocacy remain, and ongoing role clarification is needed.     

Preservice teacher use of learning and instructional design principles

Although many instructional technologists have suggested that teachers should be trained in using instructional design models, few studies have been conducted to determine if teachers can be successful in acquiring and applying these models. The purpose of this study was to examine preservice teacher success in acquiring and applying principles of learning and instructional design. Preservice teachers enrolled in a professional teacher preparation program were taught the essentials of learning and competency-based instruction and were required to plan a lesson using these concepts. Results indicate that most of the preservice teachers were successful in acquiring and using the principles of learning and instructional design.     

The understanding heart: aging parents and their favorite children

This paper compares the characteristics of adult children who provide comfort and sympathy and serve as confidants to parents with those whom parents perceive as disappointing. Interview information from 117 couples having children who had left home was analyzed using aggregate and intrafamilial strategies. The latter analyses compared the characteristics of the selected child with those of her or his sibs instead of comparing the aggregate of selected children with the aggregate of their siblings. Differences in the findings from the 2 techniques are discussed. The findings confirmed the importance of daughters who live nearby as understanding children. More important than proximity among the factors influencing parental judgments on disappointing and understanding children were intergenerational shared interests and values.     

Planning text structure as a way to improve students' writing from sources in the compare–contrast genre

The aim of this study was to improve 7th- and 8th-grade students' (N = 83) compare–contrast reports when writing from sources. An instructional unit was designed and implemented for this purpose. It focused on increasing students' knowledge of compare–contrast text structure and on having students memorize and use a table to plan the structure of their reports. There was a large effect size of instruction, such that students in the instruction group made far greater gains in the holistic and structural quality of their writing (from pretest to posttest) than students in the control group.     

The Impact of Scaffolding and Student Achievement Levels in a Problem-based Learning Environment

This study examined how scaffolds and student achievement levels influence inquiry and performance in a problem-based learning environment. The scaffolds were embedded within a hypermedia program that placed students at the center of a problem in which they were trying to become the youngest person to fly around the world in a balloon. One-hundred and eleven seventh grade students enrolled in a science and technology course worked in collaborative groups for a duration of 3 weeks to complete a project that included designing a balloon and a travel plan. Student groups used one of three problem-based, hypermedia programs: (1) a no scaffolding condition that did not provide access to scaffolds, (2) a scaffolding optional condition that provided access to scaffolds, but gave students the choice of whether or not to use them, and (3) a scaffolding required condition required students to complete all available scaffolds. Results revealed that students in the scaffolding optional and scaffolding required conditions performed significantly better than students in the no scaffolding condition on one of the two components of the group project. Results also showed that student achievement levels were significantly related to individual posttest scores; higher-achieving students scored better on the posttest than lower-achieving students. In addition, analyses of group notebooks confirmed qualitative differences between students in the various conditions. Specifically, those in the scaffolding required condition produced more highly organized project notebooks containing a higher percentage of entries directly relevant to the problem. These findings suggest that scaffolds may enhance inquiry and performance, especially when students are required to access and use them.