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Forum: Biostatistics

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

  1. 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: 0
    • Views: 111
    05-20-2015, 10:28 PM Go to last post
  2. 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: 72
    05-20-2015, 08:52 PM Go to last post
  3. 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: 317
    05-17-2015, 09:31 PM Go to last post
  4. 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: 177
    05-14-2015, 08:49 AM Go to last post
  5. 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: 92
    05-14-2015, 05:33 AM Go to last post
  6. 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: 124
    05-12-2015, 04:34 AM Go to last post
  7. 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: 130
    05-11-2015, 03:54 PM Go to last post
  8. 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: 295
    05-10-2015, 04:15 PM Go to last post
  9. 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: 378
    05-05-2015, 04:23 PM Go to last post
  10. 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: 114
    05-05-2015, 10:07 AM Go to last post
  11. 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: 416
    05-05-2015, 09:39 AM Go to last post
  12. 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: 225
    05-04-2015, 09:26 AM Go to last post
  13. 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: 127
    05-03-2015, 01:05 PM Go to last post
  14. 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: 98
    05-03-2015, 11:52 AM Go to last post
  15. 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: 240
    05-02-2015, 12:21 AM Go to last post
  16. 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: 122
    05-01-2015, 02:00 PM Go to last post
  17. 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: 214
    05-01-2015, 12:29 PM Go to last post
  18. 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: 209
    04-30-2015, 08:09 AM Go to last post
  19. 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: 293
    04-28-2015, 01:15 PM Go to last post
  20. 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: 174
    04-26-2015, 03:54 PM Go to last post
  21. 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: 150
    04-25-2015, 11:22 AM Go to last post
  22. 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: 112
    04-25-2015, 03:37 AM Go to last post
  23. Average individual correlations or perform 1 set of correlations

    First of all thanks for your time reading this post. I got some issue with correlation analysis that I am not able to solve at all as for more...

    Started by aloik‎, 04-24-2015 07:44 AM
    • Replies: 0
    • Views: 153
    04-24-2015, 07:44 AM Go to last post
  24. biological relevance of low fold changes in gene/protein expression?

    Hello, I have proteomic data pertaining to organs of rats treated chronically with a low dose of a chemical. The rats have developed pathologies...

    Started by VladimirM‎, 04-22-2015 11:21 AM
    • Replies: 0
    • Views: 174
    04-22-2015, 11:21 AM Go to last post
  25. Spearmans Correlation Doubt

    Hello! I have some doubts about Spearmans's Correlation and I would like to ask your help! I have 5 variables (3 independent and 2 dependent) and...

    Started by pedro90‎, 04-16-2015 05:30 AM
    • Replies: 1
    • Views: 290
    04-17-2015, 03:44 PM Go to last post
  26. Can subject be a factor?

    Let's say we have an epidemiology research with 5 subjects (for simplicity): John, Mike, Andy, Frank and Philip. They contacted meningitis and their...

    Started by nick01‎, 04-15-2015 10:09 AM
    error term, two-way anova, zero degrees of freedom
    • Replies: 2
    • Views: 240
    04-15-2015, 11:52 AM Go to last post
  27. what to do with duplicate subjects in data set

    I have 2 subjects in my data set that I suspect are duplicates-also the data is highly unusual, do I exclude then from analysis? According to the...

    Started by darcymagoo@yahoo.com‎, 04-12-2015 04:32 PM
    • Replies: 1
    • Views: 247
    04-12-2015, 08:53 PM Go to last post
  28. pairwise associations-which model to run?

    Should I perform multiple linear regression for the following homework question? Perform the necessary analyses for creating “Table Q1: Pairwise...

    Started by darcymagoo@yahoo.com‎, 04-12-2015 04:29 PM
    • Replies: 0
    • Views: 174
    04-12-2015, 04:29 PM Go to last post
  29. Question weighting of aligned subsequences by their length

    I have a pool of subsequences, each one associated with a probability (and other properties that you don't need to know) that quantifies how...

    Started by tevang‎, 04-11-2015 10:13 AM
    alignment, probability, sequence, weighting
    • Replies: 0
    • Views: 192
    04-11-2015, 10:13 AM Go to last post
  30. Taking the Mean of a Mean

    Hello, I have 2 groups, each with 3 subjects and each subject with 5 replicate values. I want to compare the means of the measured values between...

    Started by Universal Exports‎, 04-10-2015 11:28 AM
    • Replies: 0
    • Views: 181
    04-10-2015, 11:28 AM Go to last post
  31. How to format a null hypothesis without statistical analysis

    I had to complete a research project that involved a cell membrane protein, and I had to find if there was a correlation to its presence on cells and...

    Started by Orange91‎, 04-09-2015 12:35 PM
    • Replies: 1
    • Views: 255
    04-09-2015, 01:34 PM Go to last post
  32. How to compare IRRs of two different groups?

    Hello all, thanks in advance for your help. This is my question: I have a structured panel data for repeated measure over time per single person ...

    Started by Ralph84‎, 04-09-2015 08:54 AM
    • Replies: 3
    • Views: 237
    04-09-2015, 11:45 AM Go to last post
  33. How to analyze my longitudinal data

    Hi all, I've been struggling to figure out the best way to analyze my data. I randomized participants to one of 3 groups and had them complete my...

    Started by capobl‎, 04-08-2015 10:32 AM
    • Replies: 2
    • Views: 249
    04-08-2015, 01:58 PM Go to last post
  34. Question Cox regression application in business/finance

    Hi all, I hope this is the right forum to ask as cox regression is usually use by bio-statisticians. My research is about companies which...

    Started by roslina‎, 04-07-2015 11:10 AM
    cox regression, spss, time dependent
    • Replies: 4
    • Views: 333
    04-07-2015, 10:29 PM Go to last post
  35. sample size recalculation mid-trial based on unplanned look at data

    what is the current thinking on sample size recalculation mid-trial based on unplanned look at the data. suspect futility and want to either stop...

    Started by msecic‎, 08-28-2014 12:52 PM
    • Replies: 1
    • Views: 423
    04-07-2015, 10:12 AM Go to last post
  36. Canonical Correspondance Analysis interpretation

    Hi , I'm trying to do a CCA on two data sets , species dataset vs environment variables dataset the results are in the attached png . ...

    Started by chmilblik‎, 04-05-2015 10:05 AM
    • Replies: 1
    • Views: 198
    04-05-2015, 11:13 AM Go to last post
  37. Multiple imputation and ROC curve anlaysis

    Hi, I have searched extensively for a solution to the following problem, without success. I have used multiple imputation on SPSS 22 to create 5...

    Started by CE479‎, 03-31-2015 04:25 PM
    • Replies: 9
    • Views: 523
    04-02-2015, 12:36 PM Go to last post
  38. Block desing with several datapoints

    Hey, I'm a PhD students and confronted with the following problem, hoping someone can give me an advise. For my research I had to use a more...

    Started by pech.13‎, 04-02-2015 08:57 AM
    block design, visualization
    • Replies: 0
    • Views: 130
    04-02-2015, 08:57 AM Go to last post
  39. Total complications in both groups

    Hi, I have the following question: In my study I compare two kinds of surgery options. Group A has 9 patients and group B has 6 patients. When...

    Started by chabby‎, 03-31-2015 08:28 AM
    events
    • Replies: 9
    • Views: 336
    04-01-2015, 01:04 PM Go to last post
  40. Sample size calculation for non-inferiority and superiority

    Dear all, I am little bit confused with dual statements which I read in the literatures and books. Some says that Non-inferiority studies requires...

    Started by kumarnaidu‎, 03-26-2015 06:30 AM
    • Replies: 4
    • Views: 379
    03-27-2015, 09:48 PM Go to last post
  41. Comparing rates of hospital episodes in different groups

    Hi there, I'm trying to compare the rates of hospital admissions in different groups. For example: 200,000 people live in the local area, and...

    Started by lewerdan‎, 03-24-2015 07:18 AM
    • Replies: 6
    • Views: 380
    03-27-2015, 11:32 AM Go to last post
  42. Discretization of a continuous variable

    He guys, I'm analyzing a research regarding patients and their risk factors for developing a certain side effect. If i enter age as a continous...

    Started by XPeriment‎, 03-26-2015 06:06 AM
    • Replies: 1
    • Views: 195
    03-26-2015, 06:20 AM Go to last post
  43. Three way anova for repeated measure

    Hi all, I am struggling with how to properly fit a three way anova using STATA. It keeps giving me this error message "could not determine...

    Started by Ralph84‎, 03-24-2015 01:47 PM
    • Replies: 5
    • Views: 381
    03-25-2015, 07:33 AM Go to last post
  44. Futility analysis sample size

    Hello, I have been asked to determine the sample size needed to demonstrate futility in a small study. I suggested going the "traditional route" and...

    Started by jcr‎, 03-24-2015 09:55 AM
    futility, interim, sample size, stopping, type 2 errors
    • Replies: 2
    • Views: 191
    03-24-2015, 10:10 AM Go to last post
  45. One or Two Way ANOVA?

    Hi all, Just had a quick question regarding whether or not I should be using a one or two way ANOVA to see the effect of caffeine on heart rate....

    Started by squath‎, 03-20-2015 10:55 PM
    anova, biostats, trials
    • Replies: 4
    • Views: 385
    03-23-2015, 11:10 AM Go to last post
  46. Comparing proportions

    I am planning ahead before starting an experiment and want to be sure that I can analyze the results statistically. I have two related questions,...

    Started by mpal‎, 03-21-2015 12:27 PM
    • Replies: 1
    • Views: 275
    03-23-2015, 09:22 AM Go to last post
  47. Determining whether the exponent of an allometric equation = 3

    I have derived several allometric (exponential) equations in the form Y=bX^a These relate body mass of wildebeest (Y) to linear body measurements...

    Started by Gnu‎, 03-17-2015 03:30 AM
    • Replies: 6
    • Views: 470
    03-23-2015, 08:56 AM Go to last post
  48. Question types of chi-square statistics

    :) hi all I want to know types of Chi-square statistics and their applications. Such as Pearson x2 and mantel-haenzel x2 and x2trend and ... .

    Started by hol‎, 03-19-2015 01:38 PM
    • Replies: 2
    • Views: 247
    03-20-2015, 01:35 AM Go to last post
  49. Comparing Measured and Predicted body Mass - Can I use the T-Test

    I have measured the body mass (Mb) of several wildebeest in kg. I have also measured other parameters including Girth (G), Length (L) and shoulder...

    Started by Gnu‎, 03-17-2015 03:15 AM
    • Replies: 3
    • Views: 317
    03-17-2015, 06:45 AM Go to last post
  50. Fat percentage affecting diet

    Need some help with some biostats. Studying for a final right now. I think i need to do a one-way anova and a post hoc comparison. I also need a full...

    Started by silentdogood‎, 03-16-2015 08:55 PM
    • Replies: 0
    • Views: 236
    03-16-2015, 08:55 PM Go to last post
  51. Comparing two %, what test can I use?

    Good afternoon forum fellows, I am currently conducting a prospective research study at my hospital. I haven't used my stats skills in awhile and...

    Started by jyw003‎, 03-15-2015 02:52 PM
    • Replies: 3
    • Views: 299
    03-16-2015, 07:49 PM Go to last post
  52. Range, does it matters ?

    Hello I am slightly confused about something. I will try to illustrate. Let's say that if one takes a medication to treat a condition, the...

    Started by Yankel‎, 03-15-2015 03:21 PM
    • Replies: 3
    • Views: 332
    03-16-2015, 03:18 AM Go to last post
  53. Mantel's Chi 2 test - how to perform

    Hello dear users, I have a question about Mantel's Chi 2 test and you are my last hope :). I want to perform Mantel's Chi 2 in SPSS but cant find...

    Started by badibad‎, 03-13-2015 02:14 PM
    • Replies: 3
    • Views: 317
    03-14-2015, 02:20 PM Go to last post
  54. Interpreting hierarchical logistic regression results

    I conducted a hierarchical logistic regression examining the association among several different types of childhood adversities, mental disorders,...

    Started by elaine1827@yahoo.com‎, 03-13-2015 09:48 PM
    • Replies: 1
    • Views: 234
    03-13-2015, 10:31 PM Go to last post
  55. Question Comparing means with zero-inflated data in SPSS

    Hi everybody, I whish to know how to compare means with zero-inflated data. I tried to perform an ANOVA test but obviosuly it's impossible since...

    Started by Reset85‎, 03-12-2015 12:09 PM
    anova, generalized linear models, spss, zero inflated
    • Replies: 0
    • Views: 262
    03-12-2015, 12:09 PM Go to last post
  56. T test on whole sample or on averages

    Background: Consider the following experiment: There are two groups of subjects, Group A have been treated with a drug that affects the muscle...

    Started by theblackalchemist‎, 03-10-2015 04:55 AM
    • Replies: 3
    • Views: 373
    03-12-2015, 06:25 AM Go to last post
  57. Repeated measures in a GLM, do I need to use a GLMM?

    Hi guys, So I have finished an experiment where I had 11 cages of mice building nests with 3 different materials. Each cage was given a material...

    Started by Daveinci‎, 03-10-2015 09:30 AM
    • Replies: 1
    • Views: 296
    03-10-2015, 02:30 PM Go to last post
  58. what stats to use?

    Dear All, As I am not experienced in stats I would like to ask for some stats suggestions for a study. study one: control impact with one...

    Started by jg.marine‎, 03-10-2015 11:56 AM
    biostatistics, ecological statistics, permanova, r software, unbalanced
    • Replies: 0
    • Views: 190
    03-10-2015, 11:56 AM Go to last post
  59. Measurement error in binary outcome variable for a case-control study

    I am currently working on a case-control study on a rare disease using a large patient database. Using conditional logistic regression I will...

    Started by marsh_randy‎, 03-05-2015 11:57 AM
    • Replies: 3
    • Views: 381
    03-06-2015, 07:44 AM Go to last post
  60. Survival Analysis - Rate covariates

    hi all! I'm not too experienced with survival analysis, so I'm hoping to get some feed back regarding our design / study: Start Date: Date...

    Started by jamesmartinn‎, 03-05-2015 10:51 AM
    • Replies: 0
    • Views: 214
    03-05-2015, 10:51 AM Go to last post

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