Báo cáo y học: "Statistics review 3: Hypothesis testing and P values" pdf

Ngày tải lên: 12/08/2014, 19:22

... a population from a representative sample. A common next step in data analysis is calculation of P values, also known as hypothesis testing. Hypothesis testing is generally used when some comparison is ... reviews. Keywords hypothesis testing, null hypothesis, P value Available online http://ccforum.com/content/6/3/222 greater, just by chance if the null hypothesis is true. B...

Ngày tải lên: 12/08/2014, 18:21

... Ordered Discrete Continuous Ventilatory support Severity of illness Days in ICU Blood pressure Main types: In tables, shown as: Graphically shown as: Types: Examples: Table 1 Haemoglobin (g/dl) from 48 intensive care patients 5.4 ... or box and whisker plots. Tables and graphs provide a convenient simple picture of a set of data (dataset), but it is often necessary to further sum- marize...

Ngày tải lên: 12/08/2014, 18:21

... SD can be approximated by the sample SD. These assumptions, particularly the first, will generally be valid if the sample is sufficiently large. There may be occasions when these assumptions break ... the present review concentrates specifically on estimation of a population mean. Consider all possible samples of fixed size (n) drawn from a population. Each of these samples has its own mean...

Ngày tải lên: 12/08/2014, 18:21

... approximately 86 (43 per arm) and 116 (58 per arm) for P values of 0.05 and 0.01, respectively. The nomogram provides a quick and easy method for deter- mining sample size. An alternative approach ... the statistical power of the study. Put simply, this is the probabil- ity of correctly identifying a difference between the two groups in the study sample when one genuinely exists in th...

Ngày tải lên: 12/08/2014, 18:21

... data’, ‘samples and populations’, ‘hypotheses testing and P values’ and ‘sample size calculations’. Future topics to be covered include comparison of proportions, simple regression and analysis of survival ... recently published trial that compared early goal-directed therapy with standard therapy in the treatment of severe sepsis and septic shock [1]. A total of 263 patients we...

Ngày tải lên: 12/08/2014, 19:21

... ‘presenting and summarizing data’, ‘samples and populations’, ‘hypotheses testing and P values’, ‘sample size calculations’ and ‘comparison of means’. Future topics to be covered include simple regression, ... may be inappropriate. For example, non- parametric methods can be used to analyse alcohol con- sumption directly using the categories never, a few times per year, monthly, w...

Ngày tải lên: 12/08/2014, 19:21

Ngày tải lên: 12/08/2014, 19:22

... study into early goal-directed therapy in the treatment of severe sepsis and septic shock by Rivers and coworkers [5], one of the outcomes measured was in- hospital mortality. Of the 263 patients ... in- hospital mortality. Of the 263 patients who were randomly allocated to either early goal-directed therapy or standard therapy, 236 completed the therapy period with the outcomes shown in...

Ngày tải lên: 12/08/2014, 20:20

... test. 391 test the null hypothesis that there is no difference between the population survival curves (i.e. the probability of an event occurring at any time point is the same for each population). The ... each case. The authors also applied Cox’s proportional hazards analysis and obtained the results given in Table 6. These results indicate that both age and long-term oxygen therapy ha...

Ngày tải lên: 12/08/2014, 20:20