34371 - Biostatistics course Part 9 Comparison between two...

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Unformatted text preview: Biostatistics course Part 9 Comparison between two means Dr. Sc Nicolas Padilla Raygoza Department Nursing and Obstetrics Division Health Sciences and Engineering Campus Celaya-Salvatierra University of Guanajuato, Mexico Biosketch Medical Doctor by University Autonomous of Guadalajara. Pediatrician by the Mexican Council of Certification on Pediatrics. Postgraduate Diploma on Epidemiology, London School of Hygiene and Tropical Medicine, University of London. Master Sciences with aim in Epidemiology, Atlantic International University. Doctorate Sciences with aim in Epidemiology, Atlantic International University. Associated Professor B, Department of Nursing and Obstetrics, Division Of Health Sciences and Engineering, Campus Celaya Salvatierra, University of Guanajuato. [email protected] Competencies The reader will apply a Z test to inferences from a comparison of two paired means. He (she) will apply a Z test to inferences from two independent means. He (she) will apply t test to inferences from a mean of differences in a small sample. He (she) will apply a t test to inferences for two independent means in a small sample. He (she) will obtain a confidence interval for two independent means and for a mean of differences. Introduction Often we want to compare two groups. The statistical methods used for the comparison of two means depends on how these means were obtained. The data can be obtained from paired or not paired samples. Paired data How to obtain paired data? Paired samples occur when first measure is matched with a second measure in the same subject. For quantitative data usually occurs when there are repeated measurements on the same person. Example In a study to determine whether birth weight measurements are adequate, we compared the birth weight of newborns from a hospital in Celaya, Gto. The measurements were performed by different people, to control the measurement bias, being an observer blinded to the measurement of another observer. Non-paired data How to obtain non-paired data? We get non-paired data when observations in a sample are independent from observations in another sample. Example To study the effects of a new drug to treat the parasitic burden of Ascaris lumbricoides , patients were randomized to receive nitazoxanide (group A) and albendazole (group B). The effect of the drug in each group was measured and compared. In the analysis of paired data we calculate the difference between the first and second measurement. This gives us a sample of differences, and then apply the methods of analysis for quantitative data from one mean. Analysis of quantitative paired data When analyzing paired data, you must first calculate the difference between two measurements in the same subject....
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This note was uploaded on 02/23/2012 for the course STAT 312 taught by Professor Staff during the Fall '11 term at Rutgers.

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34371 - Biostatistics course Part 9 Comparison between two...

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