Báo cáo y học: " Statistics review 6: Nonparametric methods" docx

... risk less than 1.0 (a ‘negative’ Review Statistics review 6: Nonparametric methods Elise Whitley 1 and Jonathan Ball 2 1 Lecturer in Medical Statistics, University of Bristol, Bristol, UK 2 Lecturer ... than some hypothesized value, and considers whether this is substantially different from what we would expect by chance. If any observations are exactly equal to the hypothesized va...

Ngày tải lên: 12/08/2014, 19:21

... X 2 ,…, X n ). In other words: Review Statistics review 1: Presenting and summarising data Elise Whitley* and Jonathan Ball † *Lecturer in Medical Statistics, University of Bristol, Bristol, UK † Lecturer ... plots Unordered Ordered Discrete Continuous Ventilatory support Severity of illness Days in ICU Blood pressure Main types: In tables, shown as: Graphically shown as: Types: Exampl...

Ngày tải lên: 12/08/2014, 18:21

... approximately Normal and that the popula- tion 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 ... generally lie close to the mean, and this is reflected in the tall, narrow distribution. Review Statistics review 2: Samples and populations Elise Whitley* and Jonathan Ball † *Lectur...

Ngày tải lên: 12/08/2014, 18:21

... sufficiently small P value. Similarly, a study with high statistical power will, by definition, make iden- tification of any difference relatively easy, but this can only be achieved in a sufficiently ... apparently null result that shows no difference between groups may simply be due to lack of statistical power, making it extremely unlikely that a true difference will be correctly identifie...

Ngày tải lên: 12/08/2014, 18:21

... subsequent treatment may increase central venous oxygen saturation beyond the level expected by chance. However, the P value in isolation gives no information about the likely size of any effect. As indicated ... early goal-directed therapy may be successful in raising mean arterial pressure by between 9.3 and 18.7 mmHg. As always, it is important to interpret this finding in the context of t...

Ngày tải lên: 12/08/2014, 19:21

Ngày tải lên: 12/08/2014, 19:22

Ngày tải lên: 12/08/2014, 19:22

... community-acquired pneumonia. Crit Care Med 2004, 32:1115-1119. 2. Whitley E, Ball J: Statistics review 2: Samples and populations. Crit Care 2002, 6:1 43-148 3. Bewick V, Cheek L., Ball J: Statistics ... viable in this type of study, but RR is generally easier to interpret. The AR indicates that 14.4% of the successful outcomes can be directly attributed to the early goal-directed the...

Ngày tải lên: 12/08/2014, 20:20

... age > 65 years or ≤ 65 years, and (b) long-term oxygen therapy (LTOT) before intensive care unit admission (yes/no). The P values are for the log rank test. 391 test the null hypothesis that ... bronchiectasis Explanatory 95% confidence variables Risk ratio interval P Age (>65 years) 2.7 1.15–6.29 0.022 LTOT (yes) 3.12 1.47–6.90 0.003 LTOT, long-term oxygen therapy. ... time, the star...

Ngày tải lên: 12/08/2014, 20:20

... ed. New York, USA: John Wiley and Sons; 2000. 3. Bewick V, Cheek L, Ball J: Statistics review 7: Correlation and regression. Crit Care 2003, 7:451-459. 4. Bewick V, Cheek L, Ball J: Statistics review ... is binary (e.g. death or survival), then the probability distribution of the number of deaths in a sample of a particular size, for given values of the explanatory Review Statistic...

Ngày tải lên: 12/08/2014, 20:21