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Forum: Biostatistics

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

  1. SEM identifiability

    My question concerns a Structural Equations Modeling analysis. Should one be worried about a model being partially, over, or under identified after...

    Started by azalea‎, 06-21-2012 04:30 PM
    • Replies: 2
    • Views: 1,976
    06-28-2012, 05:41 PM Go to last post
  2. Normal distribution, do I have it?

    Hi. I've been writing here before and got some great answers. But the discussion became a bit too complicated/confusing, so I'm trying to go back...

    Started by Amana‎, 06-20-2012 03:54 AM
    • Replies: 5
    • Views: 2,962
    06-25-2012, 09:05 AM Go to last post
  3. Multiphase Survival Estimation - Data Modeling & Collinearity (Stata)

    Dear Forum Members and Statistics Ballers! I am currently trying to model a survival function for entrepreneurs, and would like to specifically...

    Started by Basti‎, 06-25-2012 04:12 AM
    interaction, multi, multiphase, phase, survival
    • Replies: 0
    • Views: 2,151
    06-25-2012, 04:12 AM Go to last post
  4. Question How can i calculate the sample size in this situation?

    I am designing a RCT between two interventions (two closure techniques of abdomen after an operation) to assess their safety, the safe intervention...

    Started by safwan‎, 06-23-2012 02:52 PM
    rct, sample size
    • Replies: 0
    • Views: 4,190
    06-23-2012, 02:52 PM Go to last post
  5. logistic regression

    In performing multivariate logistic regression with the WINKS software the output is given as a contingency table with predicted and actual outcomes...

    Started by bgaynes‎, 06-18-2012 12:50 PM
    • Replies: 2
    • Views: 2,131
    06-19-2012, 07:15 PM Go to last post
  6. Is this study clinical trial or retrospective cohort?

    Hi We have a set of patients with dental implants in their mouths. We wanna evaluate whether implants in each patient's mouth are as sensitive as...

    Started by victorxstc‎, 07-13-2011 07:43 AM
    clinical trial, retrospective study
    • Replies: 8
    • Views: 5,930
    06-19-2012, 02:18 PM Go to last post
  7. Normality violations - still use ANOVA?

    Hi all, I am having some trouble deciding which test to run for a chapter of my thesis. The brief intro is that I felled trees, cut them into an...

    Started by jhartsho‎, 06-10-2012 04:43 PM
    • Replies: 2
    • Views: 2,675
    06-15-2012, 09:18 AM Go to last post
  8. Question Parametric test results vs Non-parametric test results - interpretation help please?

    :wave: Hello, thank you so much for your help. I am currently working on an article about trends in streamflow in watersheds with different land...

    Started by Olia‎, 06-09-2012 04:39 PM
    linear regression, mann-kendall, non-parametric, parametric, results
    • Replies: 1
    • Views: 3,126
    06-15-2012, 08:03 AM Go to last post
  9. Sensitivy/specificity - I'm confused

    Hi All, I'm thinking about Sens vs Spec, like in the worked example here: http://en.wikipedia.org/wiki/Sensitivity_and_specificity but there...

    Started by Bas van Dijk‎, 06-11-2012 04:45 AM
    • Replies: 6
    • Views: 2,479
    06-12-2012, 02:57 AM Go to last post
  10. Proper statistical test

    I am doing a very simple assay to determine if biofilms are reduced when treated with a compound. Every time I run the assay I run an untreated...

    Started by rudy‎, 06-01-2012 11:06 PM
    • Replies: 1
    • Views: 1,921
    06-10-2012, 05:01 PM Go to last post
  11. Question How to analyze significant within, nonsignificant between?

    Hi everyone, hopefully this is in the right forum. I ran a mixed between-within subjects ANOVA in SPSS to see whether habitat affected the change...

    Started by Ateguava‎, 06-08-2012 02:49 PM
    • Replies: 2
    • Views: 1,958
    06-09-2012, 12:18 PM Go to last post
  12. analysis using multiple complex surveys

    Hi, I've posted a couple times before - hadn't gotten replies but have kept plugging away. I thought I'd give it one more try with updated...

    Started by birdsong‎, 06-07-2012 10:08 AM
    • Replies: 0
    • Views: 1,759
    06-07-2012, 10:08 AM Go to last post
  13. Question [Anova using R] Likely need help setting up a multi way ANOVA, open to other options

    I am analyzing the data from an MRI experiment where we tested a new contrast agent against two control agents in mice with tumors. The experiment...

    Started by EAlexWaters‎, 06-05-2012 06:26 PM
    anova, biology, glm, mri
    • Replies: 0
    • Views: 1,141
    06-05-2012, 06:26 PM Go to last post
  14. Cox PH model results

    Hi all, When I run a simple Cox proportional hazards model with one categorical variable with 3 levels...1) No pulmonary hypertension, 2) Passive...

    Started by mostater‎, 06-05-2012 10:54 AM
    • Replies: 3
    • Views: 3,369
    06-05-2012, 02:28 PM Go to last post
  15. Exclamation Variance of a corrected regression coefficient

    Ppl I really need help! Please, help me solve it: Consider the model Yi = b0 + b 1Xi +ei e_i~N(0,s^2_e) iid X_i_N(m_x,s^2_x) iid Z_i = X_i +...

    Started by Arttemus‎, 06-04-2012 03:10 PM
    delta method, regression coefficient, reliability ratio
    • Replies: 0
    • Views: 1,260
    06-04-2012, 03:10 PM Go to last post
  16. 3 study areas - changes in incidence/prev over time within AND between study areas?

    Hi everyone, I just thought it's easiest if I go through my research plan and the aim to put things into context. I've been told one thing by one...

    Started by wernie‎, 06-01-2012 11:44 PM
    prevalence incidence
    • Replies: 0
    • Views: 2,065
    06-01-2012, 11:44 PM Go to last post
  17. diagnostic testing and sample size calculation

    Hello everyone, I did a study evaluating 2 screening tools (questionnaires) compared to a reference in the same sample of patients. So all the...

    Started by noob‎, 05-19-2012 03:17 PM
    • Replies: 4
    • Views: 10,033
    05-31-2012, 06:22 PM Go to last post
  18. using chi square test with data having uncertainties

    Hello, I am interested in comparing proportions between two populations. For example, let's say in one box of 100 marbles there are 20 blues,...

    Started by birdsong‎, 05-30-2012 11:12 AM
    • Replies: 0
    • Views: 1,265
    05-30-2012, 11:12 AM Go to last post
  19. Question Nonparametrics, which test should I use?

    Hello. I am a veterinary student who is stuck in some statistics. I am doing an experiment with mice. I have two treatment groups and have...

    Started by Amana‎, 05-11-2012 08:12 AM
    3 Pages
    1 2 3
    • Replies: 30
    • Views: 6,746
    05-30-2012, 09:12 AM Go to last post
  20. NAMCS, NHAMCS and SPSS

    Hello, I am analyzing NAMC and NHAMCS ambulatory health care survey data using SPSS. There are design variables in the data files that can be...

    Started by birdsong‎, 05-26-2012 05:45 PM
    • Replies: 0
    • Views: 2,166
    05-26-2012, 05:45 PM Go to last post
  21. Sample size calculation for a cluster small sample

    I am planning an evaluation of a health program that is being implemented at 42 health facilities. I will do a quasi experimental study that will be...

    Started by ozayr411‎, 05-24-2012 01:20 PM
    • Replies: 0
    • Views: 1,941
    05-24-2012, 01:20 PM Go to last post
  22. Identifying Unusual Cases in SPSS 20

    Hi, I am exploring SPSS 20 and there is this new option which seems promising: Anomaly Indices, it is in Data>Identify Unusual Cases. To me it seems...

    Started by mousme‎, 05-23-2012 05:29 AM
    • Replies: 0
    • Views: 3,752
    05-23-2012, 05:29 AM Go to last post
  23. Linear Regression question

    Dear All I am planning to perform a linear regression analysis to determine the predictor variables that best predict shallowing of the front...

    Started by SiBorg‎, 03-12-2012 01:27 PM
    • Replies: 5
    • Views: 2,667
    05-22-2012, 09:39 AM Go to last post
  24. Multivariate summary for interaction test

    Hi there, I'm trying to find some way to summarize multivariate data so that I can look at interaction terms for entire groups of molecules...

    Started by jmr‎, 05-22-2012 08:08 AM
    • Replies: 0
    • Views: 1,227
    05-22-2012, 08:08 AM Go to last post
  25. Linear Mixed Model.

    Hello, I have a question. What would be more appropriate when modeling repeated measure experiment depending from 2 groups Y~1+GROUP|ID, labels...

    Started by Mikhail‎, 05-22-2012 07:37 AM
    • Replies: 0
    • Views: 1,949
    05-22-2012, 07:37 AM Go to last post
  26. Breakpoints in multivariate analysis: GLM or regression splines

    Hello all, I've been breaking my head over the following problem for some time now, but have been unable to solve it. I'm trying to asses the...

    Started by Abubakar‎, 05-21-2012 03:49 PM
    • Replies: 0
    • Views: 2,534
    05-21-2012, 03:49 PM Go to last post
  27. Help! Awkward hypothesis testing

    Hello, I desperately need some help with my project... If someone could help me, I would be very very grateful! I am comparing the different...

    Started by 87che87‎, 05-20-2012 05:51 PM
    • Replies: 1
    • Views: 1,771
    05-20-2012, 06:10 PM Go to last post
  28. help with ROC curve analysis

    Hi there, I know this is my first post, but tried looking on the forum and couldn't find a specific answer to my question. I'm using SPSS 17 to...

    Started by LightsEternity‎, 05-15-2012 10:58 PM
    • Replies: 2
    • Views: 5,426
    05-20-2012, 05:02 AM Go to last post
  29. Use of intraclass correlation coefficient

    Hi, I have two measures of the same construct for each subject but using two different methods that use different scales, if they were measuring the...

    Started by nicklt‎, 04-07-2012 09:22 AM
    • Replies: 2
    • Views: 2,538
    05-19-2012, 03:10 PM Go to last post
  30. Standardized Mortality Ratios

    Hello, I am trying to find out how to calculate a pooled SMR and 95% CI. For example, in a study there is a SMR and 95% CI presented for men, and a...

    Started by epistudent24‎, 05-18-2012 09:04 PM
    • Replies: 2
    • Views: 2,503
    05-18-2012, 09:16 PM Go to last post
  31. Linear Mixed Model: which model to use?

    Hello, I try to compare the effect of chronic disease and disease activity on several clinical test (T1,....T10). Data were collected...

    Started by Mikhail‎, 05-18-2012 10:30 AM
    • Replies: 0
    • Views: 1,570
    05-18-2012, 10:30 AM Go to last post
  32. Help! Confidence intervals for means of cluster level proportions in cluster RCT data

    I am working on a project doing some descriptive analysis of secondary outcomes collected during a cluster randomised trial and would appreciate some...

    Started by caninth‎, 05-16-2012 10:22 AM
    • Replies: 0
    • Views: 2,532
    05-16-2012, 10:22 AM Go to last post
  33. not sure how to analyse multivariate dataset

    Heya, There are 3 substances of interest and I'd like to show the variation in how they occur in 3 cellular fractions and maybe how that relates...

    Started by Craigledee‎, 05-15-2012 03:22 PM
    • Replies: 0
    • Views: 1,477
    05-15-2012, 03:22 PM Go to last post
  34. Mixed Model for repeated measures

    Hello I ran a mixed model for a repeated measures analysis and I need some help interpreting the output. To start with, how do I interpret the...

    Started by NN_STAT‎, 05-12-2012 12:36 PM
    • Replies: 11
    • Views: 5,338
    05-15-2012, 12:51 PM Go to last post
  35. Control Chart?

    I have been working on a project relating to sepsis data for about a few months now and really could use some help with statistical side of things. ...

    Started by Medic49‎, 05-09-2012 12:33 AM
    • Replies: 2
    • Views: 1,682
    05-14-2012, 02:07 PM Go to last post
  36. Interaction Term Statistically Significant in Full Model, but not Reduced

    As a preface, I had been taught to assess the interaction term prior to higher end analyses. Figuring out whether or not you have to stratify your...

    Started by ryc‎, 05-08-2012 04:50 PM
    interaction term, ordinal logit
    • Replies: 1
    • Views: 3,366
    05-10-2012, 08:56 PM Go to last post
  37. Post Treating Heteroskedasticity in Logistic regression

    I want to fit a probit model: Phi^-1(p)=aln(x)+b The Pearson residuals appear to be heteroskedastic as confirmed in the attached figures. The...

    Started by YAnna‎, 05-04-2012 08:23 PM
    • Replies: 1
    • Views: 3,264
    05-09-2012, 03:45 PM Go to last post
  38. Random Effects

    Hello I have a conceptual question. If I have data, in which I have 2 factors, 1 is a fixed effect (i.e., the level are the only levels) and 1...

    Started by NN_STAT‎, 05-08-2012 02:02 AM
    • Replies: 0
    • Views: 1,846
    05-08-2012, 02:02 AM Go to last post
  39. Binary Logistic regression with multiple variables, identify effect of each variable?

    i am doing a binary logistic regression using multiple categorical variables to get a probability output: The dependant variable being case or...

    Started by jongwook0712‎, 04-27-2012 01:35 PM
    • Replies: 5
    • Views: 3,442
    05-07-2012, 04:37 PM Go to last post
  40. Need help here

    Ok so i got a bunch of data here and i'm a little confused how to go about it. let's say we have 4 rivers : river 1,2,3,4. Rivers 1,2 are in river...

    Started by newguy‎, 05-07-2012 10:31 AM
    • Replies: 2
    • Views: 1,635
    05-07-2012, 01:34 PM Go to last post
  41. How to determine if a linear regression best fit is significantly different from 1:1

    Hello, I am comparing data obtained by two different methods that I've plotted and gotten a linear best fit line for, and I'd like to find out if...

    Started by microbegirl77‎, 05-01-2012 11:50 PM
    • Replies: 3
    • Views: 2,825
    05-04-2012, 10:21 AM Go to last post
  42. Sample Size -- Help Please

    Dear all I was wondering if I might ask for your scrutiny on my sample size calculation! I am beginning a trial to investigate if ultrasound is...

    Started by ortho‎, 05-01-2012 06:42 PM
    • Replies: 3
    • Views: 2,397
    05-02-2012, 04:09 PM Go to last post
  43. Multivariate Analysis?

    Novice stat person disclaimer :) I'll try to describe my situation the best I can. I have 100 patients. I have an initial categorical grade...

    Started by mark605‎, 05-01-2012 08:01 AM
    • Replies: 1
    • Views: 1,263
    05-01-2012, 08:19 AM Go to last post
  44. sample size

    Hi I am writing my proposal, actually presenting it tomorrow and am still confused about how to calculate the sample size My sampling method is...

    Started by Besucher‎, 04-30-2012 09:14 PM
    • Replies: 2
    • Views: 2,067
    05-01-2012, 07:57 AM Go to last post
  45. comparation of one proportion with four others

    Hello, I am analysing data on invasive species, and there is one particular part that I might need some help with. Here is the situation: I...

    Started by Jasmien‎, 04-27-2012 09:45 AM
    • Replies: 1
    • Views: 1,664
    04-29-2012, 02:37 AM Go to last post
  46. assumptions linear regression - model validation process

    Hello, again another question :-) I used a simple linear regression, and want to check whether this was a wise choise, so I am checking the...

    Started by Jasmien‎, 04-28-2012 03:51 PM
    • Replies: 3
    • Views: 3,437
    04-29-2012, 02:22 AM Go to last post
  47. Poisson regression

    Hi, I read that Poisson regression is used when the dependent variable is a "count". But what if both the dependent and the independent variables...

    Started by Jasmien‎, 04-28-2012 05:06 AM
    poisson regression
    • Replies: 3
    • Views: 2,358
    04-28-2012, 11:20 AM Go to last post
  48. Comparing signal amplitude across multiple timepoints– what method should I use?

    Hi there, I am working on a research project looking at the effect of mood on brain response during visual perception. 20 volunteers participated...

    Started by panichem‎, 03-30-2012 03:25 PM
    • Replies: 4
    • Views: 44,126
    04-26-2012, 11:00 AM Go to last post
  49. PCA - To check

    Hi I got a data set and tried my hand in doing PCA using SPSS and for the same set of data carried out PCA by using matlab program (first...

    Started by amydany1011‎, 04-14-2012 01:46 PM
    matlab, pca, spss
    • Replies: 3
    • Views: 3,470
    04-26-2012, 10:53 AM Go to last post
  50. What if events also have factors, not only the studied subjects!!

    Hello everyone... despite my a little knowledge in survival analysis and its available models.... I have the following question: What I know that...

    Started by shaker82‎, 04-15-2012 12:44 PM
    cox, hazard, survival
    • Replies: 1
    • Views: 2,094
    04-26-2012, 10:45 AM Go to last post
  51. cox regression v. kaplan-meier

    hi everyone! thanks in advance for your help! i'm studying whether the presence of high v. low hormone levels (of several different hormones)...

    Started by cayetano‎, 04-10-2012 09:05 AM
    kaplan-meier, spss, survival
    • Replies: 4
    • Views: 26,343
    04-26-2012, 10:41 AM Go to last post
  52. Sample size?

    Hello, Question sample size: 60% difference in the proportion of lymphocytes is expected between the dialysis group(32%) and patient with...

    Started by silim‎, 04-26-2012 06:38 AM
    • Replies: 0
    • Views: 2,476
    04-26-2012, 06:38 AM Go to last post
  53. Sample size?

    Hi, trying to help a friend and I can't find any formulae that directly relate the parameters needed. I need to know the sample size required for...

    Started by meelek‎, 04-11-2012 07:14 AM
    • Replies: 2
    • Views: 2,150
    04-25-2012, 09:55 AM Go to last post
  54. Kruskal-Wallis, Log-Transformation, and Comparing Ratios

    Hi, I am trying to make a statistical comparison between 4 groups. Each group is a set of ratios of two variables (% of sample cells in my mouse...

    Started by rpj2004‎, 04-19-2012 10:21 PM
    • Replies: 1
    • Views: 4,416
    04-24-2012, 03:34 PM Go to last post
  55. Bacterial pathogen trend question

    I have a statistics query that I am hoping that someone can help with. I have a series of E. coli data taken from two sites one quarterly, one...

    Started by banjowolf‎, 04-23-2012 03:15 AM
    • Replies: 0
    • Views: 1,483
    04-23-2012, 03:15 AM Go to last post
  56. Statistics for Repeatability/Reproducibility

    Hi all, I originally posted this in another forum, but in retrospect thought it might be better for this one. I'm new to this site and seeking...

    Started by microbegirl77‎, 04-19-2012 12:01 AM
    • Replies: 2
    • Views: 3,165
    04-20-2012, 07:46 PM Go to last post
  57. Image analysis for pathology

    My aim is to find difference in the expression of protein X in different areas of human carcinoma. I have 12 specimens (=patients), which are stained...

    Started by kriloru‎, 04-18-2012 07:23 AM
    • Replies: 1
    • Views: 1,292
    04-18-2012, 11:31 AM Go to last post
  58. binary logistic regression interpretation of results

    Hi all, I am new to the forum and I am also new to statistic (taking my 2nd course). I am having trouble to interpret results from a binary...

    Started by Jathank‎, 04-16-2012 12:42 AM
    • Replies: 1
    • Views: 2,246
    04-17-2012, 09:51 PM Go to last post
  59. Variable selection SVM and CART?

    Hey, i am taking an applied statistics course and have a question related to an analysis of a data set. I am observing a great degree of positive...

    Started by ia88‎, 04-17-2012 05:59 AM
    cart, svm
    • Replies: 0
    • Views: 1,725
    04-17-2012, 05:59 AM Go to last post
  60. Holm-Bonferroni for dolphin data after Mann-Whitney U

    Hi! Need help from all you experts on how to perform Holm-Bonferroni correction after having done some Mann-Whitney U tests on my data on river...

    Started by cristiancjb‎, 04-11-2012 04:38 AM
    • Replies: 0
    • Views: 2,777
    04-11-2012, 04:38 AM Go to last post

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