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Forum: Biostatistics

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

  1. 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, Today 10:54 AM
    • Replies: 4
    • Views: 70
    Today, 11:44 AM Go to last post
  2. 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: 4
    • Views: 134
    Yesterday, 01:31 PM Go to last post
  3. 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: 143
    06-29-2015, 02:02 PM Go to last post
  4. 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: 104
    06-25-2015, 01:10 PM Go to last post
  5. 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: 53
    06-25-2015, 09:48 AM Go to last post
  6. 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: 0
    • Views: 61
    06-25-2015, 05:18 AM Go to last post
  7. 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: 107
    06-24-2015, 02:00 PM Go to last post
  8. 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: 237
    06-23-2015, 06:11 PM Go to last post
  9. 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: 103
    06-23-2015, 01:49 PM Go to last post
  10. 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: 65
    06-23-2015, 01:35 PM Go to last post
  11. 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: 165
    06-21-2015, 10:09 PM Go to last post
  12. 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: 157
    06-19-2015, 06:16 AM Go to last post
  13. 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: 134
    06-18-2015, 02:10 PM Go to last post
  14. 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: 195
    06-17-2015, 07:15 AM Go to last post
  15. 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: 128
    06-17-2015, 05:38 AM Go to last post
  16. 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: 228
    06-17-2015, 02:21 AM Go to last post
  17. 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: 130
    06-16-2015, 12:04 PM Go to last post
  18. 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: 182
    06-15-2015, 02:41 PM Go to last post
  19. 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: 188
    06-13-2015, 05:41 AM Go to last post
  20. 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: 248
    06-12-2015, 07:28 PM Go to last post
  21. 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: 142
    06-12-2015, 05:02 PM Go to last post
  22. 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: 179
    06-12-2015, 04:38 PM Go to last post
  23. 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: 212
    06-11-2015, 02:12 AM Go to last post
  24. 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: 85
    06-10-2015, 06:45 AM Go to last post
  25. 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: 126
    06-09-2015, 10:19 AM Go to last post
  26. 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: 209
    06-08-2015, 01:17 PM Go to last post
  27. 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: 204
    06-08-2015, 11:06 AM Go to last post
  28. 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: 202
    06-07-2015, 02:48 AM Go to last post
  29. 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: 199
    06-06-2015, 01:25 PM Go to last post
  30. 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: 177
    06-04-2015, 04:23 AM Go to last post
  31. 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: 199
    06-03-2015, 09:48 PM Go to last post
  32. 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: 114
    06-03-2015, 12:54 PM Go to last post
  33. 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: 263
    06-02-2015, 03:55 PM Go to last post
  34. 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: 102
    06-02-2015, 03:19 PM Go to last post
  35. 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: 86
    06-02-2015, 03:15 PM Go to last post
  36. 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: 17,171
    06-01-2015, 05:19 AM Go to last post
  37. 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: 206
    05-29-2015, 06:15 AM Go to last post
  38. 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: 324
    05-26-2015, 06:17 AM Go to last post
  39. 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: 334
    05-24-2015, 06:24 AM Go to last post
  40. 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: 172
    05-20-2015, 08:52 PM Go to last post
  41. Adjustment for Odds Ratios

    At present, I am working on a meta-analysis that observes the effect of physical activity for a disease (i.e. cancer). For each study we have used...

    Started by jle‎, 05-13-2015 06:24 PM
    • Replies: 10
    • Views: 440
    05-17-2015, 09:31 PM Go to last post
  42. Normal versus non-normal - presentation of results in publication

    Dear all Can anyone help me with the following question: I have a outcome variable that is compared for different grouping variables. For some of...

    Started by sternchen‎, 05-14-2015 04:48 AM
    • Replies: 3
    • Views: 252
    05-14-2015, 08:49 AM Go to last post
  43. Adjustment for confounders for testing equality of variance

    Dear all I wonder if there is a method that allows to adjust for confounding variables when testing for the equality of variances. I am comparing...

    Started by sternchen‎, 05-14-2015 05:06 AM
    • Replies: 1
    • Views: 150
    05-14-2015, 05:33 AM Go to last post
  44. Kruskall-Wallis/Dunn or Mann-Whitney to compare communities along an area?

    Hi, I would like to know your opinion about the best statistical approach to use in the following case: - 10 sampling points distributed along an...

    Started by GSousa‎, 05-12-2015 04:34 AM
    • Replies: 0
    • Views: 187
    05-12-2015, 04:34 AM Go to last post
  45. Smile Comparing groups/sites---need advice identifying variables and appropriate tests

    Hi, thank you for reading this and your potential input. This is a research study. I examined the prevalence of parasites in one insect species...

    Started by ecologist‎, 05-11-2015 03:54 PM
    chi square test, fisher's exact test, glmm, logistic regression
    • Replies: 0
    • Views: 190
    05-11-2015, 03:54 PM Go to last post
  46. Paired or unpaired data and questions about test with >2 groups

    Hi guys! I am here for some help with my statistics. I am currently working on a small project involving the expression of surface markers on cells...

    Started by Ilarja‎, 05-06-2015 03:18 AM
    mann whitney u test, paired data
    • Replies: 2
    • Views: 362
    05-10-2015, 04:15 PM Go to last post
  47. Wilcoxon test for statistical significance

    Hi guys, I have a simple question (sry for the probably imprecise formulation, I never went to a statistics class) Assume we have a population...

    Started by Stats_Newbie‎, 05-04-2015 03:15 PM
    • Replies: 5
    • Views: 434
    05-05-2015, 04:23 PM Go to last post
  48. Goodness of Fit of Time Series Prediction

    I am an academic neuroscientist working on the following project: I am attempting to determine the evoked response of a sensory nerve (time series in...

    Started by AngryWaffles‎, 05-05-2015 10:07 AM
    • Replies: 0
    • Views: 164
    05-05-2015, 10:07 AM Go to last post
  49. Significance testing among groups of time series data

    I have produced 2 groups of time series data. Each group contains 100 time series, each of which is a solution to an ordinary differential equation...

    Started by ELMC‎, 11-01-2014 12:26 PM
    • Replies: 1
    • Views: 470
    05-05-2015, 09:39 AM Go to last post
  50. Comparing Treatments for Spinal Cord Injury

    Hi Guys. First post in this forum (actually, in any statistics forum). I am not from an English speaking country, so you may find some grammatical...

    Started by LucasConzatti‎, 05-03-2015 05:33 PM
    anova, repeated measure anova
    • Replies: 4
    • Views: 288
    05-04-2015, 09:26 AM Go to last post
  51. ROC curve after logistic

    Hello all. I have a dataset of around 700 subjects. I wanted to test whether the blood values of a protein are associated to a certain disease and...

    Started by Ralph84‎, 05-03-2015 10:56 AM
    • Replies: 1
    • Views: 172
    05-03-2015, 01:05 PM Go to last post
  52. Making sense of the directionality parameter

    Hello, This post has been cross-posted here. I fail to delete the current post to leave only the other post open. Feel free to delete this post if...

    Started by Remi‎, 05-03-2015 11:52 AM
    articles, dispersion parameter, intuition, logistic regression
    • Replies: 0
    • Views: 138
    05-03-2015, 11:52 AM Go to last post
  53. Comparing the Power and Effect Size from Different Studies

    Hi there Talk Stats Community, I am an undergraduate research assistant. Currently I am doing research on a project, and our results have...

    Started by mtm3123‎, 05-02-2015 12:21 AM
    comparison, effect size, power
    • Replies: 0
    • Views: 384
    05-02-2015, 12:21 AM Go to last post
  54. Advice on appropriate test on proportions with three factors with replication

    I am planning a study with three factors (salinity, parasite type and species). Can anyone suggest an appropriate statistical test? I am wondering if...

    Started by luhar‎, 05-01-2015 02:00 PM
    • Replies: 0
    • Views: 158
    05-01-2015, 02:00 PM Go to last post
  55. Calculate Incidence rate for disease with fertility/mortality data

    I am trying to calculate disease incidence in a certain country. I have the number of cases detected over 10 year period. The disease affects...

    Started by notimer‎, 04-28-2015 03:38 PM
    biostatistics, incidence rate, population statistics
    • Replies: 2
    • Views: 267
    05-01-2015, 12:29 PM Go to last post
  56. Transforming interaction coefficients in odds ratio (logistic regression)

    Hello everyone. :wave: First of all, sorry for my english, I am not english mother tongue. Second, sorry for my stats knowledge, I'm not a...

    Started by silviezza‎, 04-29-2015 11:28 AM
    • Replies: 2
    • Views: 261
    04-30-2015, 08:09 AM Go to last post
  57. One sample study design - Multivariate methods?

    Good Day, I am planning a one sample study of 230 patients. I am thinking of using the one sample t-test and the binomial test to perform...

    Started by tyronm20‎, 04-25-2015 09:47 AM
    • Replies: 5
    • Views: 347
    04-28-2015, 01:15 PM Go to last post
  58. How to compare samples of different sizes to look for a correlation

    Hello :) I'm hoping to find somebody that can give me some advice with my Statistics. I carried out a study on birds diet. My results show...

    Started by Alycw‎, 04-26-2015 03:54 PM
    • Replies: 0
    • Views: 221
    04-26-2015, 03:54 PM Go to last post
  59. How to estimate transition probabilities in the absence of individual patient data?

    What I tried so far is to read of the survival curves given in clinical trials with Plot Digitizer, with months ((t)months) as the X axis and...

    Started by iknownothing‎, 04-25-2015 11:22 AM
    • Replies: 0
    • Views: 196
    04-25-2015, 11:22 AM Go to last post
  60. Dunn's Multiple Comparison Test - Graphpad

    Hey, So I worked with non-parametric data (more than 3 groups) so I did the Kruskal-Wallis test to compare these groups. To see which group...

    Started by biomed‎, 04-25-2015 03:37 AM
    • Replies: 0
    • Views: 170
    04-25-2015, 03:37 AM Go to last post

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