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Category Archives: Clinical Trials

Nonparametric Methods of Estimating Survival Functions


Of the three survival functions, survivorship or its graphical presentation, the survival curve, is the most widely used. Examples include product-limit (PL) method of estimating the survivorship function by Kaplan and Meier, life-table analysis, relative survival rate, five-year surival rate, and corrected survival rate. Product-limit method is applicable to small, moderate, and large samples. However, […]

Why the Odds Ratio Can Be Used as an Estimate for Relative Risk in a Case-Control Study


The data in a case-control study represent two samples: The cases are drawn from a population of people who have the disease and the controls from a population of people who do not have the disease. The predictor variable (risk factor) is measured, and the results can be summarized in a 2 X 2 table […]

Conceiving the Research Question and Developing the Study Plan


The research question is the uncertainty that the investigator wants to resolve by performing his/her study. There is no shortage of good research questions, and even as we succeed in answering some questions, we remain surrounded by others. Clinical trials, for example, established that treatments that block the synthesis of estradiol (aromatase inhibitors) reduce the […]

Outline of A Study


This is the one-page study plan of a project carried out by Valerie Flaherman, MD, MPH, begun while she was a general pediatrics fellow at UCSF. Most beginning investigators find observational studies easier to pull off, but in this case a randomized clinical trial of modest size and scope was feasible, the only design that […]

Evaluate The Article About Therapy (Randomized Trials)


Section 1 How Serious Is The Risk of Bias? Did Intervention and Control Groups Start With The Same Prognosis? Consider the question of whether hospital care prolongs life. A study finds that more sick people die in the hospital than in the community. We would easily reject the naive conclusion that hospital care kills people […]