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Forum: Biostatistics

Epidemiology and biostatistics, public health research. GLM, logistic regression, survival analysis, clinical trials.

  1. Delta aproach for binomial data with a lot of zeros

    Dear friends, I will like to ask if someone ever used any package in R to model binomial glm for the presence-absence representation of the data,...

    Started by panas‎, 01-31-2014 05:43 AM
    • Replies: 3
    • Views: 2,336
    01-31-2014, 08:14 AM Go to last post
  2. Need help with a clinical analysis

    I am a physician with minimal stats background. I had a stats question for the people on this forum. We are measuring the "brightness" of...

    Started by ZRAD1200‎, 01-28-2014 09:54 PM
    • Replies: 1
    • Views: 1,783
    01-29-2014, 12:19 AM Go to last post
  3. Two-step cluster analysis

    I used two-step cluster analysis in SPSS to cluster my data since I have both continuous and categorical variable. The Silhouette measure show...

    Started by cwjcwjcwj‎, 01-28-2014 09:33 PM
    • Replies: 0
    • Views: 2,561
    01-28-2014, 09:33 PM Go to last post
  4. Need help with analysing count data with lots of zeros

    Hello all, I'm a bit rusty on my stats so please be gentle with me as I might not always understand the terminology :) I have a problem I am...

    Started by Smurfben‎, 01-27-2014 10:44 AM
    • Replies: 2
    • Views: 1,838
    01-27-2014, 12:36 PM Go to last post
  5. Data input for coxph(Surv analysis

    Dear friends, I would like to ask this quite easy question regarding the data format for a coxph frailty model.

    Started by panas‎, 01-27-2014 11:22 AM
    coxph, data, survival analysis
    • Replies: 0
    • Views: 1,545
    01-27-2014, 11:22 AM Go to last post
  6. Degrees of Freedom for Random Effects

    Hi, I am looking at the example which appears in this R page: http://stat.ethz.ch/R-manual/R-devel/library/survival/html/frailty.html ...

    Started by ledzep‎, 04-17-2012 01:03 PM
    • Replies: 5
    • Views: 8,845
    01-27-2014, 09:50 AM Go to last post
  7. testing for overlapping window types in protein sequences

    Dear community members, I have a problem to solve from data in the protein universe. I am working with the sum total of all ~30K proteins for a...

    Started by anandksrao‎, 01-26-2014 12:06 PM
    hypothesis testing, multiple testing, overlapping
    • Replies: 0
    • Views: 1,380
    01-26-2014, 12:06 PM Go to last post
  8. Study design? Diagnostic Errors

    Hello all, I am designing a study and wondering if you might help me with the design from a statistical perspective please? I am studying...

    Started by kerulian‎, 01-24-2014 12:37 PM
    study design error test
    • Replies: 1
    • Views: 1,493
    01-24-2014, 05:23 PM Go to last post
  9. Kruskal Wallis or Friedman test

    Hello everybody :wave:, I have the following experimental setup and would need advise on how to evaluate the data. I extracted monocytes from...

    Started by Faol‎, 01-15-2014 09:39 AM
    • Replies: 2
    • Views: 2,285
    01-23-2014, 07:01 AM Go to last post
  10. Semi Parametric/Fully Parametric and Non-Parametric - When do you prefer which?

    Hello there! I'm trying to write a portion of an essay covering the question "Under what circumstances might a semi-parametric specification be...

    Started by Bbfornow‎, 01-20-2014 07:39 PM
    • Replies: 1
    • Views: 1,838
    01-20-2014, 10:44 PM Go to last post
  11. Continuous exposures for matched case control study

    Hi Continuous exposures for matched case control study - this is not the typical design you would usually see in epidemiological studies. I have...

    Started by gnlebasi‎, 01-20-2014 04:58 AM
    case control; matched
    • Replies: 0
    • Views: 1,125
    01-20-2014, 04:58 AM Go to last post
  12. One sample clustered continuous data

    Hello all, I asked here a question not long ago regarding binary clustered data. Now I have a different yet similar question. I have one sample...

    Started by NN_STAT‎, 01-20-2014 04:22 AM
    • Replies: 0
    • Views: 1,178
    01-20-2014, 04:22 AM Go to last post
  13. Diffusion and Beta distr.

    The Pdf-file 'Number 4' contains a small problem that I have thinking a lot about. How can I show that it can be approximated by a diffusion...

    Started by ole‎, 01-15-2014 06:33 AM
    • Replies: 0
    • Views: 2,391
    01-15-2014, 06:33 AM Go to last post
  14. compare two bimodal distributions

    I have 16 experiments performed under different conditions and I would like to compare them between each other. Each experiment has 5-6 samples...

    Started by Lorean‎, 01-15-2014 05:35 AM
    • Replies: 0
    • Views: 3,003
    01-15-2014, 05:35 AM Go to last post
  15. Does using a prospective data set make a clinical study prospective.

    I haven't been able to find this out anywhere. I am writing a systematic review on radiation therapy toxicity and dividing works by prospective vs....

    Started by Foreverstudent‎, 01-01-2014 07:35 PM
    • Replies: 2
    • Views: 1,860
    01-13-2014, 04:54 PM Go to last post
  16. clustered data

    Hello all, I have a binary outcome (success \ failure). I have 20 subjects, half of them gave 2 samples, the others just one, so I have 30 data...

    Started by NN_STAT‎, 01-11-2014 04:07 AM
    • Replies: 6
    • Views: 2,286
    01-12-2014, 10:30 AM Go to last post
  17. Creative solution for ill-planned trial?

    Dear all, This is my first post. This is a great forum. I am facing a problem: I have some really cool health data but it was not collected from a...

    Started by Time‎, 01-10-2014 12:12 PM
    • Replies: 3
    • Views: 2,660
    01-12-2014, 07:34 AM Go to last post
  18. Exclamation Assumption of Homoscedasticity not met...Repeated measures ANOVA

    Hey guys, Student in clinical research here and in dire need of help. My study is a clinical trial with 2 treatment groups measured over 4 time...

    Started by elissa‎, 01-10-2014 11:14 AM
    anova, repeated measures, variance
    • Replies: 0
    • Views: 3,152
    01-10-2014, 11:14 AM Go to last post
  19. Comparing percent suppression of proliferation

    Hi all, I am study a cell type (MDSC) that are known to suppress the proliferation of immune cells (mainly T cells). In order to test for...

    Started by JessR417‎, 01-09-2014 01:31 PM
    cpm, percent, proliferation, ratio, suppression
    • Replies: 0
    • Views: 1,734
    01-09-2014, 01:31 PM Go to last post
  20. Simulation of blood glucose

    Hello all, I would like to make a simulation model of blood glucose using a real dataset of patients' blood glucose levels. I have thousands...

    Started by tonytheviking‎, 01-03-2014 06:44 PM
    • Replies: 4
    • Views: 3,385
    01-04-2014, 04:05 PM Go to last post
  21. Question Determining an indirect confidence interval for justifying a non-inferiority margin

    I need to establish the efficacy of a test treatment (T) by means of an indirect comparison to placebo (P). Therefore a study of T vs. reference (R)...

    Started by AVoelp‎, 01-03-2014 05:22 AM
    confidence intervals, indirect effects, non-inferiority
    • Replies: 0
    • Views: 1,594
    01-03-2014, 05:22 AM Go to last post
  22. ROC cutoff value

    Hello everyone While most of you is in vacation it came a cross my mind to post a question that I am trying to answer How to identify the cutoff...

    Started by drmohamedbekheit‎, 01-01-2014 09:45 AM
    • Replies: 8
    • Views: 3,930
    01-02-2014, 12:05 PM Go to last post
  23. Cox PH model vs KM curves

    Hello, everyone! I applied Cox PH model to my data and the results I got was quite reasonable. But I am a bit confused because it seems that...

    Started by dandy‎, 12-28-2013 06:22 AM
    • Replies: 2
    • Views: 2,416
    01-01-2014, 02:14 PM Go to last post
  24. Net reclassification improvement

    Dear All Would you please advice me on how to get the R plugin for SPSS (free) I need to run the net reclassification improvement and I do not...

    Started by drmohamedbekheit‎, 01-01-2014 12:11 PM
    • Replies: 0
    • Views: 2,894
    01-01-2014, 12:11 PM Go to last post
  25. Dependent variable from ratio counts. That's discrete? If yes, which test for low Ns?

    Hi all, I have a rather specific question, I somehow don't seem to be able to find the answer to. So I work on biological tissue, where I count the...

    Started by solar‎, 12-18-2013 10:21 AM
    biological statistics, discrete random variables, statistical tests
    • Replies: 2
    • Views: 2,065
    12-29-2013, 05:04 AM Go to last post
  26. Power analysis in a repeated measures desgin

    Hi We are planning a randomised clinical trial treating patients with either an active drug or placebo in 20 weeks. We measure the dependent...

    Started by MBJ‎, 12-22-2013 03:38 PM
    covariance structure, mixed models, power calculation, repeat measures
    • Replies: 0
    • Views: 1,562
    12-22-2013, 03:38 PM Go to last post
  27. Need help with linear mixed modeling in SPSS

    So I've looked a quite a few tutorials and forums to see if anyone has posted something similar to the dataset I'm analyzing, and it doesn't seem...

    Started by kernsaid‎, 12-17-2013 03:11 PM
    epidemiology, linear mixed model, spss
    • Replies: 0
    • Views: 1,783
    12-17-2013, 03:11 PM Go to last post
  28. multinomial logistic regression: independent continuous variable,help to interpretate

    Hello I was running this statistic but I have some problems to interpretate it my dependent variable is categorical and it expresses difference...

    Started by Rerun‎, 12-16-2013 09:46 AM
    • Replies: 4
    • Views: 2,647
    12-16-2013, 11:27 AM Go to last post
  29. Analysis of single arm study

    Hello all, I need some help choosing how to analyze my data. I have a single arm study, i.e., a study testing a new treatment, but not against...

    Started by NN_STAT‎, 12-13-2013 01:45 PM
    • Replies: 1
    • Views: 2,379
    12-15-2013, 12:05 PM Go to last post
  30. Interpreting Number Need to Treat

    I work out manually that my number needed to treat was 170. I then used a program to work out confidence interval of -0.0191 to 0.0073. ...

    Started by umirin‎, 12-08-2013 10:21 AM
    • Replies: 2
    • Views: 1,803
    12-14-2013, 10:15 AM Go to last post
  31. GEE vs. GLMM

    hello all, I have a question, related to my previous post, but deserves it's own post. Lets say I have a binary dependent variable, with one...

    Started by NN_STAT‎, 12-13-2013 01:57 PM
    • Replies: 2
    • Views: 7,349
    12-13-2013, 03:12 PM Go to last post
  32. Can I assume these are independent?

    Hello! Trying to resolve in my mind a small dilemma. I'm assessing the risk factors for blood loss in surgery. The data come from an...

    Started by ted‎, 12-11-2013 06:21 PM
    biostatistics, independence, sas
    • Replies: 2
    • Views: 2,119
    12-12-2013, 11:32 AM Go to last post
  33. Log-Rank/Kaplan Meier Analysis. Group Size..

    Hallo! I am currently working on a research project and want to evaluate the loss of a chromosome versus survival. I have data on 22 Patients and...

    Started by vincemd‎, 12-10-2013 07:30 AM
    • Replies: 0
    • Views: 1,304
    12-10-2013, 07:30 AM Go to last post
  34. Calculate 95% CI for hazard ratio

    this post is no longer available

    Started by statsbug‎, 12-09-2013 03:46 PM
    • Replies: 1
    • Views: 2,395
    12-09-2013, 04:06 PM Go to last post
  35. Im lost. Im in serious need of assistance in Statistics

    Hi everyone Im Christopher from the Philippines. I am working on a research right now. One of the objectives of my study is to know the significant...

    Started by cmdparrilla‎, 12-08-2013 01:26 AM
    • Replies: 0
    • Views: 1,667
    12-08-2013, 01:26 AM Go to last post
  36. Question Heeeelp! Two-way ANOVA (repeated measurments)?

    Dear experts I have used blood cells from 3 different persons to do an experiment. I have treated the cells with 8 different treatments with one...

    Started by Sly‎, 12-07-2013 05:06 PM
    • Replies: 0
    • Views: 1,967
    12-07-2013, 05:06 PM Go to last post
  37. Which regression should I use?

    I am trying to analyze the following research question. I hypothesize that smoking status increases risk of heart attack but this effect is...

    Started by vicvan‎, 12-06-2013 07:07 PM
    • Replies: 3
    • Views: 1,876
    12-06-2013, 07:26 PM Go to last post
  38. is log rank test appropriate here?

    Hi all, I am doing cognitive testing and the subjects have 20 possible trials to reach criterion (90% accuracy). In my spreadsheet, I have it laid...

    Started by dbh21486‎, 12-05-2013 09:47 AM
    • Replies: 2
    • Views: 2,328
    12-06-2013, 07:25 AM Go to last post
  39. Sample size calculation

    Hi all, if got the a question concerning sample size calculation: When doing a sample size calculation for a randomized clinical trial for...

    Started by sternchen‎, 11-19-2013 05:26 PM
    power, sample size
    • Replies: 1
    • Views: 1,556
    12-06-2013, 02:50 AM Go to last post
  40. I cant figure out how to design this..please help

    i attached the quesiton..please give some insights... thanks

    Started by tank520‎, 12-03-2013 07:45 PM
    • Replies: 1
    • Views: 1,297
    12-05-2013, 05:35 PM Go to last post
  41. What statistical test is ideal for my research??

    I am doing a study on expression of cytokeratins in areas of oral lichen planus and adjacent normal tissue. my sample size is 58. the study is done...

    Started by drsamprasad‎, 12-05-2013 04:15 AM
    • Replies: 1
    • Views: 1,557
    12-05-2013, 04:42 PM Go to last post
  42. "Is there a sig. difference in amount of subunits between 2 groups according to age"

    Hello! I think I've said it all in the title. I need to run right statistics to answer my question. I guess I have 2 independent variables (age in...

    Started by Tamara‎, 12-03-2013 11:54 AM
    anova, linear, regression, study, variables
    • Replies: 0
    • Views: 1,230
    12-03-2013, 11:54 AM Go to last post
  43. Cox analysis to assess a variable as predictor of trend within a specific period?

    Hello to everybody! First of all thank you because you have been extremely helpful throughout :) This is my new case: I have an independent...

    Started by Rerun‎, 11-20-2013 10:23 AM
    • Replies: 2
    • Views: 983
    12-02-2013, 05:26 PM Go to last post
  44. Paired sibling data

    I'm helping with a study that is looking at gestational cytokine levels of children with neurodevelopmental disorders versus neurotypical children....

    Started by kernsaid‎, 12-01-2013 07:20 PM
    linear regression, paired data, spss 21
    • Replies: 0
    • Views: 1,569
    12-01-2013, 07:20 PM Go to last post
  45. Analysing several categories simultaneously

    Hi I want to sample several (thousands) of animals and analyse whether they have a certain biomarker or not (YES/NO). The animals will be of...

    Started by Teedjay‎, 11-30-2013 12:33 PM
    • Replies: 0
    • Views: 1,430
    11-30-2013, 12:33 PM Go to last post
  46. Help with two trends analysis

    Hello everybody, this is my first post on this site. I'm an italian (so sorry in advance for my english) immunology researcher and i'm currently...

    Started by Krigan‎, 11-29-2013 06:39 AM
    • Replies: 0
    • Views: 1,589
    11-29-2013, 06:39 AM Go to last post
  47. HIV Research: Do I want to do a cluster analysis?

    See attached image: I'm looking at the performance of HIV clinics in New York State. Performance is measured in the proportion of patients whose...

    Started by dfeller‎, 11-27-2013 11:22 AM
    • Replies: 1
    • Views: 2,208
    11-29-2013, 05:07 AM Go to last post
  48. Ordinal dependent variable and catagorical independent - which test

    Quick question for the Sages of the forum I have a study looking at patients who have been injured with a score attributed - ordinal data Each...

    Started by edmundfitz‎, 11-28-2013 04:35 PM
    • Replies: 2
    • Views: 2,048
    11-28-2013, 04:46 PM Go to last post
  49. Talking Calculating 10 year probability using hazard ratios...

    I'm a medical student. I am working on some medical research. Given 3 values (BMI, age, gender) I have a list of baseline risks for the...

    Started by mattiast‎, 11-27-2013 04:41 PM
    • Replies: 0
    • Views: 1,378
    11-27-2013, 04:41 PM Go to last post
  50. Is this possible: group passes normality, but outlier is present?!

    Hi! I have posted last night something about this issue, but now I will reformulate the question. I have data from animal study in which we had...

    Started by jelenar‎, 11-24-2013 01:26 PM
    • Replies: 3
    • Views: 1,961
    11-25-2013, 08:14 AM Go to last post
  51. Question Multiple comparison problem (one-to-many)-Protein sequence

    Dear All, I am new here and this is my first post. I have a problem where I am comparing a set of 9 protein amino acid (AA) sequences (Proteins I...

    Started by MaiaJulio‎, 11-22-2013 04:34 AM
    biostatistics, bonferroni correction, fisher exact test, multiple comparison, proteomics
    • Replies: 2
    • Views: 1,818
    11-25-2013, 03:59 AM Go to last post
  52. GLM contrast table mystry

    Dear Colleagues I hope you are all fine I ran a repeated measures analysis with two independent variables each with three levels at first I...

    Started by drmohamedbekheit‎, 11-24-2013 11:58 AM
    • Replies: 1
    • Views: 1,320
    11-24-2013, 05:48 PM Go to last post
  53. PLease, help, t-test or something else? And how :)

    HI! I have a huge problem. Those are my results from experiments: animals which ate water *i.e. control group) has these value for amount of...

    Started by jelenar‎, 11-23-2013 07:09 PM
    • Replies: 2
    • Views: 1,614
    11-23-2013, 07:18 PM Go to last post
  54. average difference in averages... ?

    Hi all, I'm hoping to get some feedback on a project I'm working on in terms of the methods we're using. I'll give a brief description of our...

    Started by jamesmartinn‎, 11-20-2013 09:20 AM
    • Replies: 4
    • Views: 2,609
    11-21-2013, 06:42 PM Go to last post
  55. How to combine experiments using Kruskal-Wallis or Wilcoxon rank sum

    Stats newbie/grad student with a question, I want to compare the statistics from multiple experiments to see if I see the same effect between...

    Started by mpalmerbio‎, 11-19-2013 07:35 PM
    • Replies: 4
    • Views: 1,758
    11-21-2013, 12:29 PM Go to last post
  56. Smile What test to compare bacterial growth in three areas with repeating variables?

    I have a dataset of number of bacterial colonies grown from 11 water samples taken from 3 different watersheds. I want to know if the land area,...

    Started by valentine35‎, 11-15-2013 10:08 PM
    • Replies: 1
    • Views: 2,098
    11-20-2013, 06:05 AM Go to last post
  57. Which test to use? Fisher exact?

    Hi all, We're studying expression of a protein from benign to primary malignant and metastatic lesions. Let's say 0/15 of the benign, 19/27...

    Started by Royelfire‎, 11-09-2013 05:32 PM
    • Replies: 1
    • Views: 1,950
    11-19-2013, 10:41 AM Go to last post
  58. comparing 2 groups (4 repetitions) - correct stat?

    Dear all, I'm currently having a lot of trouble finding the adequate statistical analysis for my current experimental data. The experiment: I...

    Started by Marcus_pocus‎, 11-14-2013 07:09 AM
    • Replies: 1
    • Views: 1,714
    11-19-2013, 10:33 AM Go to last post
  59. Thumbs down Advise on choosing statistical method

    Hi. I'm a medicine student and I'm relatively new to statistics. I'm looking at some data and I can not figure out which statistical method I should...

    Started by orangemasa‎, 11-02-2013 04:01 AM
    • Replies: 4
    • Views: 2,056
    11-19-2013, 10:26 AM Go to last post
  60. Which Test: selecting two predictors of disease outcome

    Hi I'm wondering which test I should use to analyzed my data. What I have are two groups: progressing and non-progressing patients; and I want to...

    Started by Chris4Evar‎, 11-12-2013 03:54 PM
    • Replies: 1
    • Views: 1,795
    11-19-2013, 05:51 AM Go to last post

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