Using web-based tools for teaching statistical concepts and experimentation skills
This paper describes a number of generally accessible web-based tools the authors developed over the last couple of years and used in several statistics courses, ranging from the introductory statistics course to a specialized design of experiments course. The first set of tools (VESTAC) illustrates statistical concepts, the second one (VIRTEX) consists of virtual experiments. We discuss some of our experiences with regard to the development and maintenance of these tools and their use in ex cathedra teaching sessions, in guided practice sessions and in student projects. Finally we discuss a third type of tools: distance experiments.
Virtual Experiments and their Role in Teaching Design and Analysis of Experiments
The ability to design experiments in an appropriate and efficient way is an important skill, but students typically have little opportunity to get experience. Most textbooks introduce standard general-purpose designs, and then proceed with the analysis of data already collected. Some recent textbooks (e.g. Cobb 2002, Dean and Voss 1998) stress the importance of including projects in which the students actually have to prepare, perform and analyze a real experiment. Such projects provide an invaluable experience, but are very time and resource consuming, for the student as well as for the teacher. In this paper we explore an additional tool for gaining design experience: computer based virtual experiments. What we call “virtual experiments” are software environments, which mimic a real situation of interest, and invite the user to collect data to answer a research question. The data are generated by an underlying realistic stochastic model, invisible to the user. Once the data are collected, they can be transferred to a standard statistical package. The user can train his/her design skills by relating the quality of the statistical results obtained to the data collection strategy used. A number of such environments have been implemented. The collection is called VIRTEX (VIRTual EXperiments), and is a companion to the VESTAC collection, previously developed for other statistical purposes (Darius et al. 2000). The environments are all realized in the form of JAVA applets, and are freely available on the web at http://www.kuleuven.ac.be/ucs/virtex/ . They can be run on any computer with a web browser that supports JAVA (the vaccine applet needs the SUN virtual machine). Due to the safety requirements of applets, they cannot read or write data from or to the user’s hard disk. Yet data can be exchanged with other programs through cut and paste.
High-frequency hearing thresholds: effects of age, occupational ultrasound and noise exposure
AbstractPurpose
It has been suggested that high-frequency audiometry (HFA) could represent a useful preventive measure in exposed workers. The aim was to investigate the effects of age, ultrasound and noise on high-frequency hearing thresholds.MethodsWe tested 24 industrial ultrasound-exposed subjects, 113 industrial noise-exposed subjects and 148 non-exposed subjects. Each subject was tested with both conventional-frequency (0.125–8 kHz) and high-frequency (9–18 kHz) audiometry.ResultsThe hearing threshold at high frequency deteriorated as a function of age, especially in subjects more than 30 years old. The ultrasound-exposed subjects had significantly higher hearing thresholds than the non-exposed ones at the high frequencies, being greatest from 10 to 14 kHz. This hearing loss was already significantly evident in subjects with exposure <5 years and increased with years of exposure and advancing age. The noise exposure group had significantly higher hearing thresholds than the non-exposed group at the conventional frequencies 4 and 6 kHz and at the high frequency of 14 kHz. After stratification for age, there was a significant difference between the two groups at 9–10 and 14–15 kHz only for those under 30 years of age.ConclusionMultivariate analysis indicated that age was the primary predictor, and noise and ultrasound exposure the secondary predictors of hearing thresholds in the high-frequency range. The results suggest that HFA could be useful in the early diagnosis of noise-induced hearing loss in younger groups of workers (under 30 years of age).
