Báo cáo y học: "Statistics review 5: Comparison of means" docx

... value gives no indication of the size of any dif- ference; it merely indicates the probability that the difference arose by chance. In order to assess the magnitude of any dif- ference, it is essential ... investigation of the data may often be sufficient in practice. If assumptions of Normality are violated, then appropriate transformation of the data (as outlined in Statistics...

Ngày tải lên: 12/08/2014, 19:21

... types of data can be represented figuratively; the two important features of a quantitative dataset (location and variability); the measures of location (mean, median and mode); the measures of ... unrepresentative of the data. Mode The mode is simply the most commonly occurring value in the data. It is not generally used because it is often not represen- tative of the data, parti...

Ngày tải lên: 12/08/2014, 18:21

... is defined entirely by its mean and SD, the following rules (rep- resented by parts a–c of Fig. 4) will always apply regardless of the specific values of these quantities: (a) 68.3% of the distribution ... previous review in this series introduced the notion of data description and outlined some of the more common summary measures used to describe a dataset. However, a dataset i...

Ngày tải lên: 12/08/2014, 18:21

... 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 large study. In practice ... 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 the...

Ngày tải lên: 12/08/2014, 18:21

... be Normally distributed, whereas the sign test only requires that they are independent of one another. Alternatively, the dis- crepancy may be a result of the difference in power provided by the ... into groups on the basis of their duration of stay. The data presented here are taken from the group of patients who stayed for 3–5 days in the ICU. The total dose of propofol administ...

Ngày tải lên: 12/08/2014, 19:21

Ngày tải lên: 12/08/2014, 19:22

Ngày tải lên: 12/08/2014, 19:22

... in the 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 ... 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 therapy...

Ngày tải lên: 12/08/2014, 20:20

... 1.054–1.474 Figure 4 The Kaplan–Meier estimates of survival for (a) 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 ... numbers of observed events in groups 1 and 2, respectively, and E 1 and E 2 the total numbers of expected events. The total expected number of events for a group is the sum...

Ngày tải lên: 12/08/2014, 20:20

... First, the importance of each of the explanatory variables is assessed by carrying out statistical tests of the significance of the coefficients. The overall goodness of fit of the model is then ... inclusion of the variables resulted in the same model, though this may not always be the case because of correlations between the explanatory variables. Several models may produce...

Ngày tải lên: 12/08/2014, 20:21