Study 2: the study of medical records

Considering a confidence level of 95% and a standard error of 5%, the study would require the inclusion of at least 385 patients to provide a valid representation of the population under investigation. However, our study takes on an additional layer of complexity as we aim to make a cross-country comparison, analysing differences within the study population. To accomplish this and maintain robust statistical power, we need to consider a power level of 0.9 and an alpha level of 0.05. These choices are essential to ensure that our study is adequately powered to detect any meaningful differences between the countries being examined. Given these criteria and assuming an effect strength (η2) of 0.015, we should aim to include a minimum of 346 patient records from each site, thus totalling 1,730 patient records for the four countries comparative analysis (France, Germany, Italy, Norway, and Spain). This larger sample size is necessary to account for the population differences and to draw meaningful conclusions about the healthcare conditions and outcomes in each country.