Modified Cluster Sampling Research Articles

The public health response to the Chi-Chi earthquake in Taiwan, 1999.

On September 21, 1999, at 1:47 a.m., an earthquake measuring 7.3 on the Richter scale struck the middle Chi-Chi region of Taiwan. The present study examines the response of the public health sector to the earthquake. A community needs assessment using modified cluster sampling was performed in shelters of Nantou and Taichung Counties five days after the earthquake struck. Twenty-five temporary medical service systems (TMSSs) conducted surveillance for selected diseases and mortality within one week post-earthquake aided by a buddy system that allowed unaffected counties to provide support to affected counties. The number of cases of acute respiratory infections and acute gastroenteritis in the affected area was higher than that of neighboring unaffected counties in the post-earthquake phase (p<0.001). Earthquake-related deaths were estimated at 2,347 deaths (death rate 116 per 100,000 population); the mean age of the decedents was 49.7 years. No significant difference was observed between males (120/100,000) and females (110/100,000) (risk ratio [RR]=1.09; 95% confidence interval [CI] 0.84, 1.42; p>0.05). The age-adjusted mortality rate was significantly higher in 1999 (odds ratio [OR]=2.11; 95% CI 1.99, 2.24) than in a comparable period in 1998. Emergency preparedness must be based on carefully conceived priorities, information, and communications, and improved capabilities must be developed to rapidly implement an emergency public health network. The emergency response to this event-consisting of TMSSs, a buddy system, and a communication system-should be considered in planning for future disaster events in Taiwan.

Patterns of antimicrobial use and antimicrobial resistance among healthy children in Bolivia.

To determine the incidence of antimicrobial-resistant, nonpathogenic Escherichia coli among healthy children aged 6-72 months in Camiri town and a rural village, Javillo, in south-eastern Bolivia. A community-based survey: stool samples were obtained from 296 healthy children selected by modified cluster sampling in Camiri and all 25 eligible children in Javillo. E. coli isolates were tested for antimicrobial susceptibility according to the standard disc diffusion method. By a questionnaire survey of 12 pharmacies and by using simulated patients, we investigated the antimicrobial availability and the usage patterns in Camiri town. In Camiri, over 90%, and in Javillo over 70% of children carried E. coli resistant to ampicillin, trimethoprim-sulphamethoxazole (TMP/SMX) or tetracycline. Overall, 63% of children carried E. coli with multiple resistance to ampicillin, TMP/SMX, tetracycline and chloramphenicol. In the simulated patients study, antimicrobials were dispensed inappropriately for 92% of adults and 40% of children with watery diarrhoea, and were under-prescribed for males with urethral discharge (67%) or females with fever and dysuria (58%). The dose and/or duration of antimicrobials dispensed was almost always too low. Our study showed a disturbingly high prevalence of carriage of nonpathogenic E. coli resistant to antimicrobials. The prevalence of resistance to ampicillin and TMP/SMX was higher than that previously reported in developing countries. The existence of a large reservoir of resistance genes in healthy individuals in developing countries represents a threat to the success of antimicrobial therapy throughout the world. Programmes to improve rational and effective drug use in developing countries are urgently needed.

Pulse polio immunization in Delhi--1995-96: a survey.

A coverage evaluation survey of the campaign for mass Pulse Polio Immunization (PPI) on 9th December, 1995 and 20th January, 1996 in Delhi was carried out using the modified cluster sampling technique and a pre-structured proforma. Six-hundred-and-nine children of under-3 age group were covered in the survey. Overall coverage for both the doses was found to be 77%. While coverage for 9th December dose was found to be 80%, it rose to 90.2% on 20th January, 1996. Coverage levels for male and female children were similar. Parental literacy was seen as a definite factor, positively affecting the coverage levels. Proportion of not covered under PPI was significantly higher in the 0-6 months age group. Television and health workers were found to be the main sources of awareness about PPI.

Use of a Modified Cluster Sampling Method to Perform Rapid Needs Assessment After Hurricane Andrew

Study objective: To rapidly obtain population-based estimates of needs in the early aftermath of Hurricane Andrew in South Florida. Methods: We used a modified cluster-sampling method (the Expanded Programme on Immunization [EPI] method) for three surveys. We selected a systematic sample of 30 quarter-mile square clusters for each survey and, beginning from a random start, interviewed members of seven consecutive occupied households in each cluster. Two surveys were of the most affected area (1990 population, 32,672) at three and ten days after the hurricane struck; one survey was of a less affected area (1990 population, 15,576) seven days after the hurricane struck. Measurements and main results: Results were available within 24 hours of beginning each survey. Initial findings emphasized the need for restoring utilities and sanitation and helped to focus medical relief on primary care and preventive services. The second survey of the most affected area showed improvement in the availability of food, water, electricity, and sanitation ( P ≤ .05). There was no evidence of disease outbreaks. Conclusion: For the first time, the EPI method provided population-based information to guide and evaluate relief operations after a sudden-impact natural disaster. An improvement over previous approaches, the EPI method warrants further evaluation as a needs assessment tool in acute disasters. [Hlady WG, Quenemoen LE, Armenia-Cope RR, Hurt KJ, Malilay J, Noji EK, Wurm G: Use of a modified cluster sampling method to perform rapid needs assessment after Hurricane Andrew. Ann Emerg Med April 1994;23:719-725.]

Preliminary report on reliability and validity of the trait form of the Depression Adjective Check List in a representative community sample

The purpose of this study was to investigate preliminary internal consistency and split-half reliability estimates of the trait form of the Depression Adjective Check List-Form E (DACL-E), as well as to validate three specific adjectives. The sample consisted of 294 residents of 17 inner-city neighborhoods of a large midwestern city, selected through a modified cluster sampling procedure. The Cronbach's alpha and split-half reliability estimates were similar in magnitude for both genders (.88 for males and .85 for females) and were at a level generally found to be reliable. Analyses of the three DACL-E adjectives--"distressed," "safe," and "active"--were related, respectively, to fear of crime (p less than .01), perception of one's safety (p less than .01), and active participation in crime prevention activities (p less than .001).

A modified cluster sampling method for estimating the bacterial density in Xanthan gum

Abstract Suppose particles are randomly distributed in a certain medium, powder or liquid, which is conceptually divided into N cells. Let pi denote the probability that a particle falls in the ith cell and Yi denote the number of particles in the ith cell. Assume that the joint probability function of the Yi follows a multinomial distribution with cell probabilities pi respectively. Take n (≤N) cells at random without replacement and put each of the cells separately through a mixing mechanism of dilution and swirl. These n cells constitute the first stage samples and the number of particles in these cells are not observable. Now conceptually divide each of n cells into M subcells of equal size and let Xij denote the number of particles in the jth subcell of the ith cell selected in the first stage; i=1,2,…,N and j=1,2,…,M. Consequently assume that the conditional joint probability function of the Xij given Yi=yi follows a multinomial distribution with equal cell probabilities. Now take m (≤M) subcells at random from each of the cells selected in the first stage sample. Assume that the numbers of particles in M×N subcells are observable. The properties of the estimator of the particle density per sample unit are investigated under the modified two-stage cluster sampling method. A laboratory experiment for Xanthan Gum Products is analyzed in order to examine the appropriateness of the model assumed in this paper.