Recent content by Markica85

Dear all, I'm analyzing a big dataset of hospitalized patients and I use Cox regression analysis to estimate associations of different parameters with survival. I have detected that there is a significant interaction between age and sex and survival, i.e. females do worse in young patients and...

Thank you, I just wanted to hear opinion like yours, but still I don't understand the real reason why both test should not be used as approaches to two different questions. What makes chi-squared illegal? It is exploratory analysis of retrospective data-set. Main stratification of renal...

I would like to say that both tests should be used for different information (assess size of proportions measured by different tests - Mc Nemar, assess distribution of proportions in two groups defined by other test - Chi squared). Two different types of contingency tables from same data. Is...

I'm doing a retrospective analysis of 70 patients with specific blood disease that were evaluated for frequency of renal dysfunction by 5 different ways. Data show that each of 5 approaches yield different frequency of renal disorder among those patients (45%, 37%, 17%, 8% and 6%). Since McNemar...

Thank you

I can also argument that biologically important difference in any of the measured relative gene expression would be at least 5 delta CT units. Largest standard deviation in measurements was 2.1 for one of the gene expressions, and given these assumptions I can calculate that my study had 100%...

Dear all, I deal with the results of a study done on 20 patients and 20 controls who were evaluated for expression of five genes using PCR - numerical variables representing gene expression levels are provided (no apriori power analyses defining sample size were done - number of participants...

Thank you

Does ROC curve analysis assume that analyzed numerical variable is normally distributed?

i would like to assess whether there is "spurious" improvement in survival due to different inclusion/exclusion of alternative-diagnoses-with-adverse-outcomes when one or other classification of disease is used. Most patients would be the same, but some will differ due to different criteria

Is there a way to compare survival of paired samples (paired samples variant of the logrank test/Cox regression)? I would like to assess difference in survival of the "same" cohort classified by two different classifications of disease. Most of patients with the disease would be the same in...

Thank You guys for your suggestions. As I found out in the meantime I should first transform my data to be able to analyze it with Poisson regression in a way that every patient-year with specific properties makes one row of data, I have to deal with optimal way to do this though. Does anyone...

Unfortunatelty this is unknown. I only have information about general followup and events some time during this period - therefore cox regression is not an option i guess

I have a retrospective clinical dataset containing one column with general follow-up time and particular columns for each unwanted outcome containing number of unwanted outcomes during follow-up period (hospitalization, transplantation, death). Since follow-up time is not outcome specific...

There is one thing bothering me for some time: What does area under Kaplan-Meier survival curve actally represent? Is there a plausible way to compare two areas under curve when for instance two curves cross late in follow-up and invalidate the use of log-rank test due to violation of...