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Forum: Biostatistics

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

  1. Several concerns about Cox regression analysis models

    Hi, I'm working a retrospective / prospective cohort study on a very rare disease (5 patients a year presenting in my institution). I have a...

    Started by Markica85‎, 07-16-2015 09:18 AM
    • Replies: 8
    • Views: 286
    Today, 10:18 AM Go to last post
  2. ROC analysis using survival data

    Dear readers, I would like to create two groups of patients depending on value of numerical parameter (like age), i.e. younger and older than 60...

    Started by Markica85‎, Today 09:44 AM
    • Replies: 1
    • Views: 43
    Today, 10:07 AM Go to last post
  3. Question How to correctly combine two binary variables into one dependent variable?

    I want to create a combined death or stroke rate binary variable. For each row (patient data), I have data for death and stroke (yes/no)...

    Started by hongh‎, Today 09:19 AM
    binary dependent variable, combine variables
    • Replies: 0
    • Views: 27
    Today, 09:19 AM Go to last post
  4. Which test should I apply?

    Hi, I have a set of of things (SNPs) which explain a percentage of variance of a trait. I got a subset of those SNPs and they explain a higher...

    Started by AleixArnau‎, Yesterday 10:21 AM
    test question
    • Replies: 1
    • Views: 82
    Yesterday, 11:37 AM Go to last post
  5. Pearsons Correlation, Two-way ANOVA, Linear Regression Test, Chi-Square Test or None

    During research, you have asked your participants whether or not they have ever experienced financial difficulties (yes or no). You have three...

    Started by robertshane‎, 07-29-2015 02:35 PM
    biostats, chi square test, linear regression, pearson correlation, two way anova
    • Replies: 1
    • Views: 79
    07-29-2015, 02:48 PM Go to last post
  6. Variable selection with longitudinal and correlated data

    Hi, I'm working with a high-dimensional medical database, with detailed monthly medication reimbursement data as well as occurence of diverse...

    Started by yohannM‎, 07-27-2015 09:31 AM
    correlated, longitudinal, penalized regression
    • Replies: 2
    • Views: 131
    07-28-2015, 03:09 AM Go to last post
  7. Multiple group stats - Protein Work - Anova or T-test

    Hi Everyone, I have a question that I'm stuck on. I think I know the correct way to do it but from what I see when I visually graph I don't believe...

    Started by 12_eggs‎, 07-27-2015 04:21 PM
    • Replies: 0
    • Views: 92
    07-27-2015, 04:21 PM Go to last post
  8. Interpretation of Mantel-Haenszel Statistics

    We have conducted an experiment with 2 groups and a dichotomous outcome on 3 occasions and for each occasion we have a 2x2 contingency table. Rather...

    Started by Andybell321‎, 07-25-2015 10:36 AM
    categorical data analysis, mantel-haenszel
    • Replies: 0
    • Views: 124
    07-25-2015, 10:36 AM Go to last post
  9. Question The Future of Clinical Trials Biostatistics - Bayesian?

    I have noticed a trend with hiring managers to vault candidates that are well versed in Bayesian analysis to the top. This is not necessarily...

    Started by PRCarpenter‎, 07-22-2015 07:03 PM
    bayesian, biostatistician, clinical trials, jobs, philosophy
    • Replies: 1
    • Views: 152
    07-22-2015, 09:14 PM Go to last post
  10. Question on statistical method

    I have a data set (attached) that I am trying to analyze, specifically I am trying to determine if the independent variables 2,3,4,5,6,7,8 is...

    Started by iamrico00‎, 07-20-2015 08:56 PM
    • Replies: 0
    • Views: 167
    07-20-2015, 08:56 PM Go to last post
  11. How to analyze proportions from large datasets

    Hello all! This question will likely reveal my lack of basic statistics knowledge, but I can't seem to find the answer in textbooks or on this forum....

    Started by skaup‎, 07-20-2015 01:01 AM
    binary outcome, nominal data, proportions
    • Replies: 1
    • Views: 130
    07-20-2015, 02:23 AM Go to last post
  12. how to interpret or report the result

    i have done a project looking at how many malpositioned nasogastric tubes were detected on doing chest radiography in patients in ICU. can i report...

    Started by tahirrehmatullah‎, 07-16-2015 07:35 PM
    • Replies: 1
    • Views: 150
    07-17-2015, 07:43 AM Go to last post
  13. General Linear Model using proportions as raw data - transformation needed?

    Hi, I have become confused in my reading of analysis of proportions. I was all set to analyse my data using a general linear model after...

    Started by DeanP‎, 07-16-2015 11:12 PM
    general linear model, proportions, unequal sampling effort
    • Replies: 0
    • Views: 151
    07-16-2015, 11:12 PM Go to last post
  14. Request for help or orientation

    Hello. I am new here and I admit I suck at statistics. I need your help on how to solve a statistical problem. Please don't give the easy answers...

    Started by JorgeMota‎, 07-16-2015 05:44 PM
    • Replies: 1
    • Views: 106
    07-16-2015, 05:46 PM Go to last post
  15. Question Request for help on choosing a statistical test to determine the efficacy of a drug

    Hi, I'm an undergraduate working on a project concerning peptides. I have data for a group of 12 peptides that were tested against 4 types of...

    Started by SeurOre‎, 07-16-2015 09:06 AM
    amp, peptides
    • Replies: 0
    • Views: 71
    07-16-2015, 09:06 AM Go to last post
  16. Question Treating Dependent Variable (Ordinal 5 item likert scale variable)

    Hi all, I had a dependent variable of fatigue score in 4 cycles and i need to test with one Independent categorical variable which had 2...

    Started by sharfras‎, 07-13-2015 04:12 AM
    • Replies: 2
    • Views: 236
    07-15-2015, 04:39 AM Go to last post
  17. Another "which tests to use?" question

    Hi all, longtime lurker, first-time poster here. Reading people's questions and answers here really helped my understanding back when I was taking...

    Started by Werewolf‎, 07-11-2015 12:17 PM
    • Replies: 0
    • Views: 186
    07-11-2015, 12:17 PM Go to last post
  18. Request for advice on what statistical test to use for research on decision times

    Basically the research we are doing involves measuring the time taken for two dolphin subjects to make their decision in a Matching-to-Sample study....

    Started by Nithya‎, 07-09-2015 08:44 AM
    • Replies: 5
    • Views: 193
    07-11-2015, 02:41 AM Go to last post
  19. A couple of questions about results in computational neuroscience

    Hi guys, This is my first time posting here. I am a medical student and I have been conducting research in computational neuroscience over the...

    Started by ilzwalrus‎, 07-09-2015 12:32 PM
    • Replies: 0
    • Views: 146
    07-09-2015, 12:32 PM Go to last post
  20. Study on prevalence of disease

    Greetings! Can someone advise me on what is the appropriate name for the retrospective study of prevalence of certain disease within patients...

    Started by mukuwa‎, 07-07-2015 12:41 PM
    • Replies: 2
    • Views: 245
    07-08-2015, 01:56 PM Go to last post
  21. Clinical trial - stratified randomization

    Hi all, There is something very basic I don't get about stratified randomization and I was hoping you might be willing to help me with. Say I have...

    Started by LeeSG‎, 06-25-2015 05:18 AM
    clinical trial, randomization
    • Replies: 2
    • Views: 301
    07-02-2015, 11:54 AM Go to last post
  22. How do I chose between sensitivity/specificity and PPV/NPV?

    I have just finished a validation study, where two specialists used the available information to classify patients according to their diseases status...

    Started by marsh_randy‎, 06-29-2015 11:56 AM
    • Replies: 5
    • Views: 305
    07-02-2015, 03:01 AM Go to last post
  23. Incongruity between t-test and 2x2 repeated measures ANOVA/gain scores t-test/ANCOVA

    Hi, it's the first time I post here. Forgive me if my English is not always correct. I want to ask about an incongruity I found when analyzing data...

    Started by Artanis‎, 07-01-2015 10:54 AM
    • Replies: 4
    • Views: 211
    07-01-2015, 11:44 AM Go to last post
  24. Power analysis for Cox PH model

    Hello, I am new here but have searched the forum before posting. I am planning a retrospective review of previously collected data. N=480. ...

    Started by mirt2013‎, 06-25-2015 09:29 PM
    • Replies: 1
    • Views: 239
    06-29-2015, 02:02 PM Go to last post
  25. sutiable study design?

    Hi everyone. I would be thankful for any helpful advice regarding a suitable study design for a planned research. I have a series of approx. 100...

    Started by aphrux‎, 06-25-2015 01:10 PM
    • Replies: 0
    • Views: 149
    06-25-2015, 01:10 PM Go to last post
  26. Cluster analysis when two domains measure the same thing

    Hi all, first of all thank you for your help in advance. I have the following problem: I would like to perform a cluster analysis on my sample...

    Started by Rerun‎, 06-25-2015 09:48 AM
    • Replies: 0
    • Views: 94
    06-25-2015, 09:48 AM Go to last post
  27. Unit of Analysis

    Hi! Trying to determine which analysis is appropriate. Let me explain: -We have access to a community hospital records on the patient level....

    Started by jamesmartinn‎, 06-24-2015 02:00 PM
    • Replies: 0
    • Views: 150
    06-24-2015, 02:00 PM Go to last post
  28. Rate ratio interpretation for large estimates

    Hi all, Just a quick question - I have many rate ratios and the 95% CIs, most of which have narrow CIs and reasonable RRs (e.g., 1.23). I've been...

    Started by wernie‎, 06-18-2015 06:23 PM
    • Replies: 6
    • Views: 299
    06-23-2015, 06:11 PM Go to last post
  29. Need help choosing a statistical method/model

    Hello, I am currently doing a study on the defensive behavior of the European Grass Snake, and I was hoping someone could help me figure out...

    Started by brittany‎, 06-23-2015 09:44 AM
    anova ecology biology, help!, linear mixed model, logistic regression, nested anova
    • Replies: 1
    • Views: 169
    06-23-2015, 01:49 PM Go to last post
  30. how does stata calculate confidence intervals for age standardised means/proportions

    Dear Stat Talkers! I'm using the following Stata command (see help mean): mean x, std(a) stdw(b) over(c) to get age-standardised mean or...

    Started by Amu‎, 06-23-2015 01:35 PM
    confidence interval, direct standardization, stata, weighting
    • Replies: 0
    • Views: 115
    06-23-2015, 01:35 PM Go to last post
  31. Identification of study design

    Hi all, I'm just trying to figure out what to call the study design for the way my research has been set up, so could use some help! I have...

    Started by wernie‎, 06-18-2015 06:37 PM
    • Replies: 2
    • Views: 216
    06-21-2015, 10:09 PM Go to last post
  32. What will be the best test to determine the significance in my study?

    The project does not have a simple design. It is planned as follows: 1. It is a longitudinal observation during 120 days in 48 subjects (with...

    Started by gomca‎, 06-19-2015 06:16 AM
    • Replies: 0
    • Views: 200
    06-19-2015, 06:16 AM Go to last post
  33. Conflicting Results Evaluating Proportional Hazards Assumption

    Hello, Currently working on a survival analysis of some lung cancer patients. I am building a Cox PH model and was working on validating the PH...

    Started by rhysticlight‎, 06-18-2015 02:10 PM
    cox, proportional hazards, survival analysis
    • Replies: 0
    • Views: 175
    06-18-2015, 02:10 PM Go to last post
  34. Randomized trial with repeated measure - which test?

    Hi, Im currently conducting a randomized placebo trial where we test the effect of one treatment on a single outcome variable. We measure the...

    Started by DrSander‎, 06-17-2015 02:16 AM
    • Replies: 3
    • Views: 242
    06-17-2015, 07:15 AM Go to last post
  35. PAF through formula or through Conditional Logistic Regression

    Hi all, In a large registry dataset of psychiatric patients, if one wants to find the excess risk of schizophrenia patients developing depression,...

    Started by Pure_Stats‎, 06-16-2015 10:07 AM
    biostatistics, conditional regression, epidemiology, medical statistics, regression model
    • Replies: 2
    • Views: 174
    06-17-2015, 05:38 AM Go to last post
  36. Meta-analysis of cross-sectional studies with both one and two study groups

    Hello, I have a question about a meta-analysis I would like to run, comparing outcome measure Y in 'patients' groups (patients) and 'healthy'...

    Started by RutgerAussie‎, 06-15-2015 10:25 PM
    • Replies: 5
    • Views: 289
    06-17-2015, 02:21 AM Go to last post
  37. separate a population into groups using 3 sets of data at once

    Hi there, I'm working on a population for which I have done 3 chemical analyses that give the concentration of different products in their tissues....

    Started by guamfr‎, 06-10-2015 01:19 PM
    multiple datasets, sample groups
    • Replies: 2
    • Views: 168
    06-16-2015, 12:04 PM Go to last post
  38. Confidence interval for person time incidence rate

    Dear everyone, I would like to estimate a 95%CI of person time incidence rate (as 45 death per 10,000 person year) Anyone knows a way to estimate...

    Started by didye‎, 06-12-2015 03:45 AM
    confidence intervals, incidence rate, kaplan meier, person-time
    • Replies: 2
    • Views: 229
    06-15-2015, 02:41 PM Go to last post
  39. Correlating bird diversity with sampled parameters like area size, elevation R-studio

    For my thesis I need to find the connection between bird diversity and a bunch of parameters we recorded in the field for each locality. The recorded...

    Started by Hanneske4‎, 06-13-2015 05:41 AM
    • Replies: 0
    • Views: 224
    06-13-2015, 05:41 AM Go to last post
  40. Power and Sample Size Calculation

    Hi, First post here--i'm having trouble figuring out how to calculate the sample size for a study I'm planning. I don't have much statistics...

    Started by alumrock12‎, 06-10-2015 03:02 PM
    • Replies: 2
    • Views: 343
    06-12-2015, 07:28 PM Go to last post
  41. how to analyse 28 blood parameters in 3 stages of the disease ?

    hello, I would like to do an analysis of 28 blood parameters in 3 stages of the disease all parameters have specific numerical values I have...

    Started by bekble‎, 06-12-2015 05:02 PM
    • Replies: 0
    • Views: 192
    06-12-2015, 05:02 PM Go to last post
  42. Logistic Regression & Interaction Term

    Hi there, I'm trying to predict whether or not a patient has a simultaneous prescription order with various variables. To make it more clear... DV...

    Started by gene2420‎, 06-12-2015 01:38 PM
    • Replies: 6
    • Views: 238
    06-12-2015, 04:38 PM Go to last post
  43. No Wald Chi2 or Prob > Chi2 value generated for logistic regression?

    I am trying to run a logistic regression analysis using STATA and get the following output: Why is no value generated for my Wald Chi2 and Prob >...

    Started by PublicHealthGuy‎, 06-10-2015 09:54 AM
    • Replies: 3
    • Views: 281
    06-11-2015, 02:12 AM Go to last post
  44. How to incorporate data from a previous trial

    Can I incorporate data from a previous trial in a new trial without any adjustment for bias (individual subject data)? If not, which is the best...

    Started by estrucida‎, 06-10-2015 06:45 AM
    prior
    • Replies: 0
    • Views: 123
    06-10-2015, 06:45 AM Go to last post
  45. Power calculation

    I am working on a study that aims to assess predictors of insufficient food intake among elderly patients. In the study I am evaluating (9)...

    Started by Rouba‎, 06-09-2015 10:19 AM
    • Replies: 0
    • Views: 164
    06-09-2015, 10:19 AM Go to last post
  46. Incidence rate in a cohort with small sample size

    I have a small cohort of people with a specific disease (n=300) and studying the incidence of a related disease (which is kind of rare and normally...

    Started by Rerun‎, 06-08-2015 05:16 AM
    incidence rate, sample size, standardization
    • Replies: 5
    • Views: 247
    06-08-2015, 01:17 PM Go to last post
  47. Basic help with stats for drug treatments

    Hi there :wave: So I haven't a clue where to start and am hoping someone on here can point me in the right direction. I'm starting to analyse my...

    Started by CEJ‎, 06-08-2015 09:16 AM
    anova, basic, normal distribution, numerical, t test
    • Replies: 1
    • Views: 323
    06-08-2015, 11:06 AM Go to last post
  48. Removing Batch Effects (with svaseq and Combat)

    Hi everyone ! :) I'm a french student, so sorry in advance for my english... I'll try to do my best :). I currently work on a data set with a...

    Started by Vanille‎, 06-07-2015 02:48 AM
    • Replies: 0
    • Views: 294
    06-07-2015, 02:48 AM Go to last post
  49. Help with glm--- Simple Logistic Regression

    Hi All! Thanks for reading. I wanted to compare month of sample collection (April, May, June, and July) to presence/absence data (coded in binary...

    Started by ecologist‎, 06-06-2015 12:39 PM
    glm, logistic regression, r code, simple regression
    • Replies: 1
    • Views: 248
    06-06-2015, 01:25 PM Go to last post
  50. interpreting logistic regression in case p=0.0 and/or p=1.0

    Hi there, I have this (fake) example: case yes no a 25 1 b 30 0 c 0 20 I want to compare the percent of "yes" in the...

    Started by eric1708‎, 06-04-2015 04:23 AM
    • Replies: 0
    • Views: 201
    06-04-2015, 04:23 AM Go to last post
  51. KM curve

    Hi all, If I have a KM curve (survival vs years) and I have the number at risk each year (as well as hazard ratio for death over a median follow up...

    Started by ahmmri‎, 06-03-2015 06:20 PM
    • Replies: 3
    • Views: 228
    06-03-2015, 09:48 PM Go to last post
  52. Presence/absence multivariate data

    Hi, I'm trying to analyse some data I've gathered from some fossils. I have about 40 different specimens and for each specimen I've recorded the...

    Started by RaskellVirmoors‎, 06-03-2015 12:54 PM
    • Replies: 0
    • Views: 162
    06-03-2015, 12:54 PM Go to last post
  53. help with comparing paired values

    Hi I have a question regarding comparing data. I have data in spss as presented here:...the list goes on for a thousand entries (ie...A, B, C, D,...

    Started by spaceprobe‎, 06-01-2015 05:01 PM
    • Replies: 2
    • Views: 305
    06-02-2015, 03:55 PM Go to last post
  54. Comparing categorical outcome variables in repeated measures design

    I am working on an observational prospective longitudinal study with a repeated measures design. The same categorical outcome is measured for five...

    Started by AlexLev‎, 06-02-2015 03:19 PM
    categorical variables, missing data, multivariate analysis, repeated measure, repeated measurements
    • Replies: 0
    • Views: 134
    06-02-2015, 03:19 PM Go to last post
  55. Comparing proportion between categorical outcome variables, repeated measures design

    I am working on an observational prospective longitudinal study with a repeated measures design. The same categorical outcome is measured for five...

    Started by AlexLev‎, 06-02-2015 03:15 PM
    categorical variables, missing data, multivariate analysis, repeated measure, repeated measurement
    • Replies: 0
    • Views: 116
    06-02-2015, 03:15 PM Go to last post
  56. 2-way ANOVA on non-normal, hetergeneous data

    I'm trying to analyze growth data from chicks, and I need to perform the equivalent of a 2-way ANOVA (2x2 design, unequal sample sizes), but my data...

    Started by mogetons‎, 05-23-2011 06:59 PM
    • Replies: 8
    • Views: 17,538
    06-01-2015, 05:19 AM Go to last post
  57. Question How do we avoid pseudoreplication while examining stickleback-gender in perch stomach

    We are working on a project were the sex of sticklebacks in perch stomachs are assesed. The question here is; how do we avoid pseudoreplication? We...

    Started by mr_blueberry‎, 05-29-2015 06:15 AM
    chi square, pseudoreplication, t-test
    • Replies: 0
    • Views: 238
    05-29-2015, 06:15 AM Go to last post
  58. Probability of association in binary variables (allergy dataset)

    Hi I am an MD analyzing a series of patients who have undergone allergy testing. For each patient (20000 in total), there are 40 tested allergens...

    Started by Mdl4487‎, 05-24-2015 03:25 PM
    • Replies: 1
    • Views: 353
    05-26-2015, 06:17 AM Go to last post
  59. Dealing with multiple confounding variables

    for example, we have 3 confounding random variables, x1, x2 and x3 with 3 different variances. If we had to treat each variable alone, we would have...

    Started by isaacadel‎, 05-20-2015 10:28 PM
    • Replies: 3
    • Views: 367
    05-24-2015, 06:24 AM Go to last post
  60. logistic regression versus PCA

    I am doing a retrospective research on breast cancer using multivariate estimates. The aim of the research is to calculate the probability of finding...

    Started by isaacadel‎, 05-20-2015 08:52 PM
    • Replies: 0
    • Views: 218
    05-20-2015, 08:52 PM Go to last post

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