On the variance of the ratio estimator

Summary In an earlier paper [Rao 1966] an exact expression for the variance of the ratio estimator under theMidzuno-Sen sampling scheme is obtained and here we study some of the interesting properties of the coefficients involved in this expression which depend on the auxiliary information. Use of these coefficients is made of in finding out an exact expression for the Bias and Mean Square Error of the ratio estimator under Simple Random Sampling With-Out Replacement (SRSWOR) scheme.     

Developing a tutoring module for presentation of computerized patient management problems

The simulation problem is one of the most commonly used formats in computer-assisted instruction (CAI). In medical education, a patient simulation problem is known as a patient management problem (PMP). A number of computerized PMP systems are currently available. However, to date, there is no record of PMP systems having been developed using artificial intelligence. This is noteworthy since artificial intelligence techniques could help in the generation of more effective and intelligent instructional systems.

This paper analyzes and evaluates existing instructional simulation software in clinical medicine in terms of effective educational design attributes. Components of effective PMP systems thus identified are incorporated into a computerized instructional system which uses artificial intelligence techniques for teaching problem-solving and diagnostic skills to undergraduate medical students.     

The effect of interstate highway on driving times and regional shopping center drawing power

Previous studies of the driving times of shopping center patrons have not examined the effect of limited access highways. This study analyzed the impact of interstate highways on the driving times of 204 shoppers at three medium-sized regional shopping centers. Those shoppers indicating usage of interstate highways to reach their shopping destinations were significantly more likely to incur travel times greater than fifteen and twenty minutes than those not using the available interstate roads. In predicting the drawing power of these shopping centers, factors besides mass were found to be useful. These include square footage of shopping goods, stores, and number of parking places.     

The main findings of the district pilot project of labour‐intensive road construction and maintenance in Botswana and the implications for similar projects in South Africa

Unemployment has been identified as one of the main problems confronting South Africa. Recently, in order to improve rural infrastructure and create employment, several pilot projects of rural road construction have been initiated in South Africa. In such a context it is considered that attention should be drawn to a pilot project carried out some time ago in Botswana to examine the potential of labour‐intensive methods in the construction and maintenance of rural roads.

The main conclusion of the pilot project was that labour‐intensive methods were viable, although attention had to be paid to several critical factors. In 1982, following its evaluation of the pilot project, the Government of Botswana decided that over the next five years the technical and organisational methods developed during the pilot project should be replicated throughout Botswana.

After a brief survey of the background to the project, the paper summarises several important features of the pilot project and its main findings. The paper closes with some comments on the implications of this pilot project for those currently underway in South Africa.     

A hospital without walls

Pacific Presbyterian Medical Center has chalked up an impressive string of successes. What's ahead? A $20 million cancer center.     

Some comparative-statics results for nonlinear input-output models of a multisectored economy,and related results for nonlinear price-demand relations

For a nonlinear version of the linear input-output model of Leontief, we consider the effect, on the vector x of total gross outputs, of changes in the components of the final-demand vector c. For example, it is shown that, for a certain important class of models, the “large-change elasticity” of any component of x, with respect to any component of c, is less than or equal to unity. Some similar results are proved concerning properties of nonlinear price-demand relations for the case in which all goods are weak gross substitutes. Unlike earlier work in this general area, we do not introduce hypotheses concerning the indecomposability or homogeneity of certain mappings. For that reason, the results are valid for the price-demand relation for a single firm, or for any collection of firms.