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PubMed1992

The use of time-series analysis to forecast bont tick (Amblyomma hebraeum) infestations in Zimbabwe.

Studying the dynamics of tick infestations on cattle is an essential step in developing optimal strategies for tick control. Successful strategic tick control requires accurate predictions of when tick infestations will reach predetermined threshold levels. In the case of Amblyomma hebraeum, earlier work has shown that there is no consistent pattern of seasonal activity. This means that a statistical model for predicting A. hebraeum infestations cannot reliably use climatic factors as the only independent variables. An alternative method is to apply time-series, or auto-regressive moving-average (ARMA), analysis which uses only the past population patterns to predict future trends. This technique was applied to a data set consisting of 108 weekly tick counts of A. hebraeum (adult males, standard females, flat females and standard nymphs), conducted at an experimental station in southeastern Zimbabwe. The ability of the ARMA models to fit and predict actual tick infestations was judged using two sets of criteria. The first set focused on the goodness-of-fit, and used the adjusted R2 values, Q statistic and the Akaike Information Criteria. The second set of criteria measured the forecasting accuracy of an estimated equation, and consisted of regressing a 9-period forecast against an actual out-of-sample data set not used in the estimation process. The root mean square error of the forecast was also considered when comparing several models for the same data set. Using these criteria, the models estimated using the ARMA technique were judged to both fit and forecast with sufficient accuracy to warrant their use in strategic tick control. Although the success of using ARMA to forecast A. hebraeum is partly due to the non-seasonal behavior of the species, the results presented here suggest that it is worthwhile exploring the use of ARMA techniques to model the dynamics of other tick species. Where independent variables exert considerable influence on the dynamics of a tick species, these variables can be incorporated into an ARMA-style model.

Animals↗

PubMed1991

Forecasting road accident casualties in Great Britain.

There is considerable interest in many countries in the way in which their annual road accident casualty totals have developed. This leads inevitably to the question of how these totals are likely to change in the future. This paper assesses national data for Great Britain from 1949-1989 and forecasts the casualty total in the year 2000 by extrapolating the long-term decline in the rate of casualties per hundred million vehicle-kilometres. This forecast is conditional on the traffic growth predicted by that year, but it is found that uncertainty over the casualty forecast derives more from the slight irregularities in the past decline in the casualty rate than from uncertainty over the traffic prediction. Despite the use of a forecasting method that is based on an unusually strong time-series model, there is still real uncertainty about forecasting casualties over a gap of only 11 years.

Accidents, Traffic↗

PubMed1979

Forecasting bed needs and recommending facilities plans for community hospitals: a review of past performance.

A university-based hospital consulting group reviewed six studies of Michigan hospitals retrospectively in 1975. The studies represented all those done between 1967 and 1971 requiring forecasts of acute bed supply and service needs. The original studies developed forecasts using empirical studies of patient origin and rigorously prepared authoritative forecasts of county populations. The 1975 review compared forecasts of population, service population, and bed need against current values and also interviewed clients to assess retrospective satisfaction with the recommendations. Although the consultants strove steadily to minimize the bed supply and base population forecasts were accurate, the studies overestimated bed needs. Further, the clients were often dissatisfied with the original recommendations, and frequently acted to exceed them. Comparing the 1975 actual with what would now be recommended by the consultant indicates that the "error" cost the communities about $50 per person per year.

Bed Occupancy↗

PubMed1980

Daily hay fever forecast in the Netherlands. Radio broadcasting of the expected influence of the weather or subjective complaints of hay fever sufferers.

The literature on local pollen counts and their significance for hay fever is reviewed and a system for forecasting hay fever is described. Such forecasts have been broadcast by radio in The Netherlands since 1977. The hay fever forecast takes the form of a prognosis (in terms of three grades) of the influence of the expected whether situation on tomorrow's course of the subjective complaints of hay fever sufferers. It is not a forecast of the pollen count. When the subjective complaints of about 150 hay fever patients were used as reference for evaluation, the forecasts proved to have been correct in 72, 85, and 88% of the cases in 1977, 1978, and 1979, respectively. The practical usefulness and the limitations of the system are briefly discussed, with emphasis on the principle that not the local pollen count but the weather should be taken as the main determinative factor for the expected subjective experiences in a group of hay fever sufferers in a certain region.

Female↗

PubMed1988

Status of menu item forecasting in dietetic education.

The status of forecasting techniques included in educational programs and the need for instructional material on this topic were investigated. A survey instrument was developed to determine which forecasting techniques were included in instructional programs. The validated questionnaire was mailed to directors of coordinated undergraduate programs or to Plan IV representatives at all universities with programs approved or accredited by the ADA. The response rate was 59%, or 156 dietetic programs. Analysis of the survey data revealed that mathematical techniques (Box-Jenkins, regression, exponential smoothing, moving average) were not taught in the majority of educational programs. Educators responded that forecasting was an important concept and that continuing education concerning forecasting techniques that may be employed in foodservice management was needed. As a result of the analysis of the data, two self-instructional modules that could be utilized by both practitioners and educators to enhance the level of practice and education were developed. Graduate and undergraduate students at 11 universities and 35 randomly selected practitioners tested the self-instructional modules. For all groups--undergraduate, graduate, and practitioners--the t-statistic was significant at the p less than .0000 level; thus the modules were effective in teaching foodservice forecasting concepts.

Dietary Services↗

PubMed1978

Menu item forecasting systems in hospital foodservice. A cost comparison of two- and three-echelon systems.

The forecasting efficiency of two- and three-echelon menu item forecasting systems was compared. Two forecasting models were used with each system, adaptive exponential smoothing and a Box-Jenkins model. The two systems were compared in terms of forecast error costs. The two-echelon system, using adaptive exponential smoothing, was recommended. This technique resulted in the lowest forecast error costs at a majority of the lead times which probably would be used most frequently. Also, this technique was the least complicated of the four techniques which were compared.

Computers↗

PubMed1998

Tools for immunization guideline knowledge maintenance. I. Automated generation of the logic "kernel" for immunization forecasting.

IMM/Def is a prototype computer program designed to facilitate the building and maintenance of a rule-based program which performs childhood immunization forecasting. An immunization forecasting program takes as input a child's immunization history and produces recommendations as to which vaccinations are due and which should be scheduled next. A significant amount of the knowledge required for immunization forecasting can be expressed in tabular form, including the parameters that indicate the minimum age when each dose may be given and the minimum intervals between doses. The choice of which of these sets of parameters apply to a particular case depends upon additional clinical logic. To perform forecasting, this logic must be applied in three temporal contexts: (1) a dose is due now, (2) a dose is not yet due, and (3) a dose must be scheduled to follow a dose which is due now. Building and maintaining this logic by hand is a formidable challenge. IMM/Def demonstrates how this task can be simplified by first defining immunization "definition logic" which can be automatically translated into if-then rules for each of the three contexts. The approach has been applied successfully to the six childhood vaccination series which are routinely administered. A key advantage is that IMM/Def allows one to have two specifications of the logic that can be examined independently and that can be cross-checked to help assure completeness, consistency, and accuracy of the logic. The paper describes how IMM/Def performs its translation and discusses several design issues and lessons learned.

Child↗

PubMed1992

International health spending forecasts: concepts and evaluation.

Health care depends on the organizational and financial decisions which constituted each national system. Since those decisions were made at various times over the preceding years under different macroeconomic conditions, current expenditures are a distributed lag function of GDP growth and inflation rates. The accuracy of forecasts from such causal econometric models are compared to exponential smoothing, moving average, and ARIMA methods. Data fro 19 OECD countries 1965-79 are used for calibration, and then ex ante forecasts are generated for 1980-87 so that actual forecast accuracy can be tested. The greatest reduction in mean absolute error was obtained with the econometric model estimated in aggregate across all 19 countries, although single-country models, exponential smoothing and international averaging were also effective. A combination of all four forecasts was more accurate than any one alone, reducing MAE by 25% relative to a constant growth projection.

Delivery of Health Care↗

PubMed1988

An assessment of the use of Bayes' Theorem for forecasting in public health: the case of epidemic meningitis in China.

A mathematical model based upon Bayes' Theorem (BT) was used to forecast the occurrence of epidemic cerebrospinal meningitis (ECM) in ten communities in North China. Reports of ECM from each ten-day period during the meningitis season and records of special population movement during 1960-82 were analysed to establish forecast models. Calibration, split-sample, random-sample selection, as well as actual forecast tests, were used to check the efficiency of the models. For all the tests, the theoretical occurrence of ECM forecast by the BT method was compared with the observational data. Since the BT method offers efficiency and convenience, it is recommended for use in planning for the prevention and control of ECM in China.

Bayes Theorem↗

PubMed1981

An evaluation of influenza mortality surveillance, 1962-1979. I. Time series forecasts of expected pneumonia and influenza deaths.

Proposed in this paper is a new method of forecasting the expected number of pneumonia and influenza deaths based on a time series analysis of the historical mortality data. Currently, the method for forecasting the expected pneumonia and influenza deaths used by the Center for Disease Control is based on regression analysis. These forecasts are used to estimate the excess deaths attributable to pneumonia and influenza. Careful comparative analysis demonstrates that the proposed method provides a more accurate forecast of pneumonia and influenza mortality than the existing method.

Adolescent↗

PubMed1990

[Daily Japanese cedar pollen forecast in Sendai].

The forecast of daily Japanese cedar (Cryptomeria japonica) pollen counts was performed in Sendai in 1987, 1988 and 1989. The expected daily maximum temperature was used as a main determinative factor, and the term "pollen index", which is a ratio of a daily pollen count to the rest of the total seasonal pollen count, was devised and proved to be closely related to the daily maximum temperature. In 1987 and 1989, the total seasonal pollen count was very low, and daily pollen counts were in the lowest of three grades, except for a few days of the middle grade. In 1988, a fairly large number of pollen grains were observed, and forecasts of low grade were made for 28 days, middle grade for 25 days and high grade for 10 days, respectively. On the other hand, the actual daily pollen counts of low grade were 36 days, middle grade, 15 days, and high grade, 12 days, respectively. The accuracy of the forecast was 67% in 1988. The reasons for errors and the assignments for the forecast were discussed.

Forecasting↗

PubMed1976

Developing a demand forecasting system for a foodservice operation.

In foodservice operations, accurate and dependable forecasts of food production demands can help control food and labor costs. A decreased incidence of menu item over- and under-production should lower scheduled labor and production time and optimize use of equipment. Each foodservice system has specified characteristics and patterns of activity. A procedure to develop, establish, control, and evaluate a forecasting system is described. The objectives of the foodservice and the proposed forecasting system must be defined. A cycle menu and historical data bases are two key inputs. It is more accurate to forecast menu item demand than diet category demand because of the complexity in categorizing multi-restricted diets. Control of the system is maintained by establishing policies and procedures and conducting routine subjective and objective evaluations.

Computers↗

PubMed1989

Forecasting mortality: a parameterized time series approach.

This article links parameterized model mortality schedules with time series methods to develop forecasts of U.S. mortality to the year 2000. The use of model mortality schedules permits a relatively concise representation of the history of mortality by age and sex from 1900 to 1985, and the use of modern time series methods to extend this history forward to the end of this century allows for a flexible modeling of trend and the accommodation of changes in long-run mortality patterns. This pilot study demonstrates that the proposed procedure produces medium-range forecasts of mortality that meet the standard tests of accuracy in forecast evaluation and that are sensible when evaluated against the comparable forecasts produced by the Social Security Administration.

Adolescent↗

PubMed1988

Stability over time in the distribution of population forecast errors.

A number of studies in recent years have investigated empirical approaches to the production of confidence intervals for population projections. The critical assumption underlying these approaches is that the distribution of forecast errors remains stable over time. In this article, we evaluate this assumption by making population projections for states for a number of time periods during the 20th century, comparing these projections with census enumerations to determine forecast errors, and analyzing the stability of the resulting error distributions over time. These data are then used to construct and test empirical confidence limits. We find that in this sample the distribution of absolute percentage errors remained relatively stable over time and data on past forecast errors provided very useful predictions of future forecast errors.

Demography↗

PubMed1988

Forecasting menu-item demand in foodservice operations.

The state of the practice in forecasting menu-item demand in foodservice operations was determined. A survey to assess the forecasting techniques utilized by foodservice directors was administered to a random sample of 834 American Dietetic Association Members with Management Responsibilities in Health Care Delivery System. Statistical analysis of the 392 responses revealed that less than 25% of the practitioners were using mathematical models in forecasting menu-item demand. Naive models were utilized by the majority of the respondents. The moving average technique was the most frequently used (14.8%) mathematical model. Approximately 75% of the practitioners indicated that continuing education is needed relative to the forecasting techniques that may be employed in foodservice management.

Food Preferences↗

PubMed1986

Population forecasts and confidence intervals for Sweden: a comparison of model-based and empirical approaches.

This paper compares several methods of generating confidence intervals for forecasts of population size. Two rest on a demographic model for age-structured populations with stochastic fluctuations in vital rates. Two rest on empirical analyses of past forecasts of population sizes of Sweden at five-year intervals from 1780 to 1980 inclusive. Confidence intervals produced by the different methods vary substantially. The relative sizes differ in the various historical periods. The narrowest intervals offer a lower bound on uncertainty about the future. Procedures for estimating a range of confidence intervals are tentatively recommended. A major lesson is that finitely many observations of the past and incomplete theoretical understanding of the present and future can justify at best a range of confidence intervals for population projections. Uncertainty attaches not only to the point forecasts of future population, but also to the estimates of those forecasts' uncertainty.

Forecasting↗

PubMed1979

A time series approach to forecasting Australian total live-births.

The relationship between classical demographic deterministic forecasting models, stochastic structural econometric models and time series models is discussed. Final equation autoregressive moving average (ARMA) models for Australian total live-births are constructed. Particular attention is given to the problem of transforming the time series to stationarity (and Gaussianity) and the properties of the forecasts are analyzed. Final form transfer function models linking births to females in the reproductive age groups are also constructed and a comparison of actual forecast performance using the various models is made. Long-run future forecasts are generated and compared with available projections based on the deterministic cohort model after which some policy implications of the analysis are considered.

Australia↗

PubMed1982

Analysis of meal census patterns for forecasting menu item demand.

The purpose of this research was to identify functional relationships between the patient census and the official institutional census recorded at midnight for hospital inpatients and for mental health patients cared for in a satellite facility at the University of Missouri-Columbia Health Sciences Center. Investigation of these relationships was necessary to provide knowledge essential for the design of a statistical menu item forecasting system. Patient census for three meals (breakfast, lunch, and supper) was compared with the midnight census, using graphical analysis and analysis of variance. Reliable patterns were identified in the patient census data which required accommodation in a mathematical forecasting model. Three forecasting design options were identified and appraised. The simplest design option and the two more complex design options forecasted identical quantities.

Dietetics↗