توضیحات محصول دانلود پاورپوینت تحقیق درمورد کوهورت (کد10685)
دانلود پاورپوینت تحقیق درمورد کوهورت
\n\n عنوان های پاورپوینت :
\nطالعات کوهورت Cohort Studies
\nInvolves comparing disease incidence over time between groups (cohorts) found to differ on their exposure to a factor of interest. Two types: • prospective • retrospective prospective cohort study begins with the selection of two groups of non-diseased animals: • exposed to a factor postulated to cause a disease • unexposed to a factor postulated to cause a disease retrospective cohort study starts when all of the disease cases have been identified. History of each study participant is carefully evaluated for evidence of exposure to the agent under investigation
\n• You can examine multiple outcomes for a single exposure, • Are very useful in examining rare exposures • Provide estimates of the absolute incidence of disease in exposed and non-exposed individuals, • Temporal sequence is logical Exposure status is recorded before disease has been identified • Provides unambiguous information about whether exposure preceded disease. • Well-suited for studying rare exposures. • Relative number of exposed and non-exposed persons in the study need not necessarily reflect true exposure prevalence in the population at large. Subjects are monitored over time for disease occurrence,
\n• Prospective cohort studies require a long follow-up period. Framingham study, 5,000 residents of framingham, massachusetts, since the early 1950’s to establish the rates and risk factors for heart disease • in the case of rare diseases large groups are necessary. • because of following forward in time likely of logistical problems, • Losses to follow-up can become an important problem. • Often quite expensive to run.
\nجدول اتفاقات Contingency table
\nمقادیر در کوهورت
\nتفسیر مقادیر کوهورت
\nمحاسبه خطر نسبی برای روستاهای واکسن خورده در فاز 22 واکسیناسیون همزمان تب برفکی (25 شهریور تا 30 مهر ) و ابتلا به بیماری از ر ( روز بعد از واکسیناسیون همگانی فاز
\nIn general, five criteria must be met to establish a cause and effect relationship
\nOf persons who attended the supper, interviewed. Forty-six persons met the case definition. Attack rates for those who did and did not eat each of items are presented in the table.
\n\nAttack rate by consumption of vanilla ice cream, Oswego, New York, April 1940
\nمسمومیت با زئولیت در گرگان
\nStatistical significance
\nFor a two-by-two table, the chi-square formula is:
\nOnce you have a value for chi-square, you look up its corresponding p-value in a table of chi-squares, such as Table 6.6. Since a two-by-two table has 1 degree of freedom, a chi-square larger than corresponds to a p-value smaller than . This means that if you have planned to the null hypothesis when the p-value is less than , you can do so if your value for chi-square is greater than .
\n \n\nقسمت ها و تکه های اتفاقی از فایل\n\n \n\nمطالعات کوهورت Cohort Studies\n\n \n\nSchematic diagram of a prospective and retrospective cohort study\n\n• You can examine multiple outcomes for a single exposure, • Are very useful in examining rare exposures • Provide estimates of the absolute incidence of disease in exposed and non-exposed individuals, • Temporal sequence is logical Exposure status is recorded before disease has been identified • Provides unambiguous information about whether exposure preceded disease. • Well-suited for studying rare exposures. • Relative number of exposed and non-exposed persons in the study need not necessarily reflect true exposure prevalence in the population at large. Subjects are monitored over time for disease occurrence,\n\nAdvantages of Cohort studies\n\n• Prospective cohort studies require a long follow-up period. Framingham study, residents of framingham, massachusetts, since the early 1950’s to establish the rates and risk factors for heart disease • in the case of rare diseases large groups are necessary. • because of following forward in time likely of logistical problems, • Losses to follow-up can become an important problem. • Often quite expensive to run.\n\nDisadvantages of Cohort studies\n\nجدول اتفاقات Contingency table\n\nمقادیر در کوهورت\n\na/a+b = Attack Rate for exposed\n\nc/c+d = Attack Rate for non – exposed\n\nAttack Rate for exposed/ Attack Rate for non – exposed = Relative risk (RR)\n\na/(a + b) / c/(c + d) = Relative risk (RR)\n\nتفسیر مقادیر کوهورت\n\nاگر خطر نسبی برابر شود یعنی ارتباطی بین تماس exposure و بیماری یا عارضه وجود ندارد.\n\nاگر خطر نسبی بزرگتر از\n\nاگر خطر نسبی کوچکتر از باشد یعنی تماس باعث محافظت از بیماری یا عارضه است یعنی تماس یک عامل محافظت Protective factor است.\n\nDeterminants\n\nبنابراین خطر نسبی Relative Risk (RR) برای روستاهای واکسن خورده برابر:\n\nIn general, five criteria must be met to establish a cause and effect relationship\n\n• Strength of association – the relationship must be clear,\n\n• Consistency – observation of the association must be repeatable in different populations at different times.\n\n• Temporality – the cause must precede the effect.\n\n• plausiblity – the explanation must make sense biologically.\n\n• Biological gradient – there must be a dose – response relationship.\n\n \n\nOf 80 persons who attended the supper, 75 were interviewed. Forty-six persons met the case definition. Attack rates for those who did and did not eat each of 14 items are presented in the table.\n\nOutbreak of gastroenteritis following a church supper in Oswego\n\nAttack rate by consumption of vanilla ice cream, Oswego, New York, April\n\nمسمومیت با زئولیت در گرگان\n\nآنها که در آب خورده بودند.\n\nآنها که در غذا خورده بودند.\n\nآنها که نخورده بودند.\n\nStatistical significance\n\nfirst step assume that the exposure is not related to disease , known as the null hypothesis.\n\nif the null hypothesis proves to be implausible, alternative hypothesis,\n\ncompute a measure of association, such as a relative risk or odds ratio.\n\ncalculate a chi-square or other statistical test.\n\nConsider p-value or probability.\n\nA very small p-value: very unlikely to observe such an association if the null hypothesis is true.\n\np-value smaller than some cutoff, such as 5%,accept alternative hypothesis\n\n \n\n \n\n۳۰ تا ۷۰ درصد پروژه / پاورپوینت / پاور پوینت / سمینار / طرح های کار افرینی / طرح توجیهی / پایان نامه/ مقاله ( کتاب ) های اماده به صورت رایگان میباشد
