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    Interim and final analysis in clinical trials

    Dear hlsmith, thank you for your response! This is a study of phase 3, main purpose is to assess efficacy. A phase 2 study showed that the study drug was reasonably safe — a very small number of adverse events with low severity. So, premature termination is not expected due to unsatisfactory...
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    Interim and final analysis in clinical trials

    Hello, I would like to know the opinion of biostatisticians with experience in clinical studies with adaptive design. I participate in a clinical trial with adaptive design as a main biostatistician. The trial is double blinded placebo-controlled study. My responsibility is to provide final...
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    comparing 3 stratified groups

    Hello, I would like to add that better way is to use measured burn sizes instead groups. In this case you would use more information for analysis and results would be more accurate.
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    Strange results of logistic regression

    Noetsi, yes, I agree. But I afraid, it returns to my first post.
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    Strange results of logistic regression

    May be, it would be better to set these predictors as text variables, as we can't order values of each of them? I tried and I received quite consistent results. By default SAS assigned binary text variables with values -1 and 1. I did it using coding: treatment values 1 and 2 as 1 and -1, gender...
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    Strange results of logistic regression

    I use SAS University Edition, the code is below: *********************************************************************************** DATA t2_work; SET t2_source; FORMAT Response 1.0; FORMAT Gender_num_F0M1_ 1.0; FORMAT Gender_num_F1M0_ 1.0; IF (responseCategory="PR" OR...
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    Strange results of logistic regression

    In 10 hours I post SAS code and output. Thank you and all responded!
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    Strange results of logistic regression

    Yes, at least 4 decimals are the same.
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    Strange results of logistic regression

    I agree that coding should not influence to results, because of it I posted this question. I put codes in 10 hours, and I don't understand what be be mistake in data. Why I should interpret the treatment effect only for one value of sex?
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    Strange results of logistic regression

    Hi everyone, I have strange results of logistic regression: The model is following: dependent: success of treatment, 0 - No, 1 - Yes, possible predictors: treatment, 1 or 2 (numeric) and sex with 2 different codes, first: (F=0, M=1), second: (F=1, M=0). If I build regression with treatment...
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    Multiplicity adjustment in correlation analysis

    hlsmith, You are right, these correlations were calculated rather for internal use. I will ask to exclude them from the article, especially since almost all coefficients are less than 0.3.
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    Multiplicity adjustment in correlation analysis

    hlsmith, thank you! Bonferroni correction is easiest, but I afraid that 99.75% CIs will be not very informative. We used Kendalls tau because the distributions of some variables were far from the normal distribution and there were some extremal values.
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    Multiplicity adjustment in correlation analysis

    Thank you for answer! Yes, all these factors have been studied. These correlations were provided only in descriptive manner, we didn't plan to do anything with it. I think the better way is to leave coefficients without correction. Especially because the purpose of the work is slightly different...
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    Multiplicity adjustment in correlation analysis

    It is a retrospective study of the causes of pain in the spine. One variable is the measured pain (VAS), the other variables are different characteristics of a patient: age, BMI, various measurements of the back condition: facet degeneration, facet sclerosis, modic changes score, Pfirrman score...
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    Multiplicity adjustment in correlation analysis

    Hi everyone, I would like to know the opinion of experienced statisticians. If I perform a correlation analysis: calculation of 20 correlation coefficients: one variable with 20 other variables, should I correct for the multiplicity? If such an adjustment is needed, then which method is most...
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    How to assess variance for sample size calculation

    Hi, hlsmith, thank you for your answer! I meant variance of combined sample. For example, efficacy variable in the 1st group has values 1, 2, 3 with mean=2 and SD=1, for the 2nd group: 11, 12, 13 with mean 12 and SD=1. Then SD for combined sample (1,2,3,11,12,13) is 5.55. Probably I don't...
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    How to assess variance for sample size calculation

    I would like to add that if mean difference between two groups is "big", then variance of combined sample should be bigger than variances of each groups, so both approaches are not appropriate.
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    How to assess variance for sample size calculation

    Hi everyone, I am going to calculate sample size for a clinical trial. I need to compare two groups by quantitative variable. I have data of a previous phase trial: Ns, means and SDs for each group. What would be better way to assess variance for using formula for sample size: to take biggest...
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    Am I using the right statistical tests?

    Sorry, I don't understand exactly your conclusion. The result is that your groups don't differ significantly. In other words, troponin doesn't influent to the death event.
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    Am I using the right statistical tests?

    yes, you can use this test without assumptions about distribution. But usually the first step is to see distribution of analysing parameters and then select data transformation by necessity and select appropriate method of analysis. In more cases in biology log transformation leads to normal...