1. 10-14-2010
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Forum: Biostatistics

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

  1. Question about sample size penalty for looking at data mid-trial

    Hi, we're running a clinical trial for a skin treatment with a medical device that has a strong effect. We are using an inter-patient control (no...

    Started by bma449‎, Yesterday 04:58 PM
    interim analysis
    • Replies: 0
    • Views: 68
    Yesterday, 04:58 PM Go to last post
  2. Help for sample size calculation

    in my prospective cohort study I will assess the serum level of a vitamin in a group of patients the normal reference serum range is 10-30 in normal...

    Started by emmyomran‎, 10-22-2016 12:04 PM
    sample size, sample size calculation
    • Replies: 1
    • Views: 124
    10-23-2016, 11:37 AM Go to last post
  3. Correlated variables in Cox model - which one is best

    Hi there, I am building a Cox model. I have two variables that are different measures of the same thing and they are therefore correlated with each...

    Started by dhmallon‎, 10-23-2016 09:27 AM
    cox proportional hazards, survival, variable selection
    • Replies: 0
    • Views: 77
    10-23-2016, 09:27 AM Go to last post
  4. HELP with data collection methods and data analysis in quantitative research : )

    I am doing a research proposal on the effect of a drug on haemorrhage growth in traumatic brain injury. My null hypothesis: TXA does not reduce the...

    Started by murrayk‎, 10-21-2016 09:11 PM
    • Replies: 1
    • Views: 96
    10-22-2016, 12:53 AM Go to last post
  5. Appropriate statistical test for HR's comparison between 2 population

    In case of 2 population, the first has HR X for the study's outcome (between the exposed and non-exposed groups), and the second has HR of Y (between...

    Started by ronitrot‎, 10-20-2016 09:03 AM
    • Replies: 1
    • Views: 114
    10-21-2016, 06:02 AM Go to last post
  6. Which statistical test to use for my data analysis

    Hi everyone, Could someone help me to know which statistics should i use for my data analysis. I did my project on "personal exposure...

    Started by Biosapien‎, 10-15-2016 01:52 PM
    • Replies: 4
    • Views: 203
    10-19-2016, 05:39 AM Go to last post
  7. Dataset for statistical analysis

    Dear all, I work in Rome for the Italian National Health Service (www.iss.it); I am currently working on a European clinic project called EMTICS...

    Started by mtallon‎, 10-17-2016 02:09 PM
    • Replies: 3
    • Views: 166
    10-18-2016, 10:26 AM Go to last post
  8. Recurrent Event Survival Analysis

    Hi there, I'm working on a research on individuals who enter financial distress using the Cox proportional hazards model. In this case the...

    Started by Mkkl‎, 10-17-2016 07:46 AM
    cox proportional hazard, recurrent events, survival analysis
    • Replies: 0
    • Views: 95
    10-17-2016, 07:46 AM Go to last post
  9. Sample Size Calculation (HELP!)

    Hi all, I wish someone could help me out. I am trying to estimate the sample size for a national health survey. From the previous report,...

    Started by chummsy‎, 10-12-2016 08:30 PM
    • Replies: 1
    • Views: 173
    10-14-2016, 05:22 AM Go to last post
  10. Best Method for Comparison of Bacterial Community Compositions

    Hi! I have curated 454 pyrosequencing data using Mothur. I have clustered reads from each sample into OTUs at a unique level. (Please see attached...

    Started by samche42‎, 10-06-2016 09:17 AM
    • Replies: 0
    • Views: 222
    10-06-2016, 09:17 AM Go to last post
  11. Markov Process to estimate time until death

    Are there any websites that show examples of data setup and SAS code using some sort of Markov model to estimate time until or probability of death?...

    Started by lancearmstrong1313‎, 10-05-2016 12:14 PM
    • Replies: 0
    • Views: 177
    10-05-2016, 12:14 PM Go to last post
  12. Which comparison of means test to use?

    I've got myself confused about which test to use. I have done a cross sectional survey exploring the difference between pain as measured with a...

    Started by jackdog3‎, 10-04-2016 06:06 AM
    • Replies: 1
    • Views: 192
    10-04-2016, 11:14 AM Go to last post
  13. comparing sensitivity, specificity, and PPV of different cohorts-is it possible?

    hello and thanks in advance for helping out! i hope that my questions will not be terribly on-profesional .. i'm trying to figure how to compare...

    Started by mrnogi‎, 10-03-2016 03:57 PM
    • Replies: 2
    • Views: 112
    10-03-2016, 11:24 PM Go to last post
  14. Poll: How do you handle subjects having very different patterns?

    Good day everyone - I am curious as to what you all do in these situations. If you are running a sleep study, and you are simply using two...

    Started by allie_moore‎, 09-26-2016 11:35 AM
    • Replies: 2
    • Views: 239
    09-26-2016, 12:14 PM Go to last post
  15. Estimating main effects in a two factorial log linear model when applied to RNA-seq

    Hi everybody, I'm going to apply multiDE, an R package for detection of DEG in multiple treatment conditions, on some RNA-seq time series data......

    Started by Fate.gh‎, 09-16-2016 02:29 PM
    log-linear, rna-seq
    • Replies: 0
    • Views: 328
    09-16-2016, 02:29 PM Go to last post
  16. Survival analysis

    Hi there, I am doing some breast cancer survival analysis on population-based registry data...I have outlined to estimate incidence trends and...

    Started by MAYA85‎, 09-15-2016 02:28 PM
    • Replies: 2
    • Views: 243
    09-16-2016, 04:20 AM Go to last post
  17. What test to use?

    Hi all, I am new to statistics. Now, I am doing a research but I don't know which test to use. Basically, I have four groups with both positive...

    Started by Upupgo‎, 09-14-2016 01:50 PM
    • Replies: 1
    • Views: 205
    09-14-2016, 02:54 PM Go to last post
  18. Question R caret package: problems understanding the functions in confusionMatrix

    Hey, I earlier posted about the problematic interpretation of PPV (positive predictive value). As there seems to be no easy solution for that I...

    Started by lilchaos‎, 09-02-2016 08:17 AM
    • Replies: 2
    • Views: 288
    09-13-2016, 01:44 AM Go to last post
  19. Talking Analysing pre- and post-treatment lactate curves

    Good morning all, Has anyone got experience with analysing lactate against power curves? I have pre- and post-treatment lactate curves for 10...

    Started by WildlifeStats‎, 09-12-2016 03:21 AM
    curve, curves
    • Replies: 0
    • Views: 137
    09-12-2016, 03:21 AM Go to last post
  20. [SPSS - post hoc analysis and Logistic regression] When the result don't line up

    I'm a medical student doing his research interneship. We're currently investigating if there's a link between motoric and mental outcome and MRI...

    Started by j0hnj0hn‎, 09-08-2016 05:34 AM
    fisher exact test, logistic regression, medicine, post hoc tests
    • Replies: 0
    • Views: 201
    09-08-2016, 05:34 AM Go to last post
  21. How to evaluate significance.

    Hi, I have 58 samples and an enrichment analysis was done to each of them. So for each sample I have a list of enriched terms. I've collected the...

    Started by MinieMe‎, 09-06-2016 11:14 AM
    • Replies: 0
    • Views: 223
    09-06-2016, 11:14 AM Go to last post
  22. ROC curve cutoff not significant, but it works

    I'm dealing with a numerical variable and its prognostic significance in a sample of cancer patients. I'm trying to find an optimal cutoff point for...

    Started by Markica85‎, 09-04-2016 07:05 AM
    • Replies: 4
    • Views: 384
    09-04-2016, 01:14 PM Go to last post
  23. How to analyze this data

    Hello, I need guidance in analyzing the outcome. I have 4 independent variables, and 2 dependent variables. The sample size is ~600. I...

    Started by reddy‎, 09-01-2016 03:22 PM
    statistical methods
    • Replies: 1
    • Views: 197
    09-02-2016, 03:46 AM Go to last post
  24. Help deciding paired vs unpaired t-test

    Hi, I am analyzing an experiment in which protein levels were examined in two different strains of bacteria. Lets call them A and B. Three...

    Started by abbey‎, 09-01-2016 01:37 PM
    comparison, t-test
    • Replies: 2
    • Views: 164
    09-01-2016, 02:19 PM Go to last post
  25. Help decide on appropriate test for experiment design

    Hello - new to the forums here! I work in cell biology and a colleague and I are designing an experiment to determine the appropriate...

    Started by Dan Kordella‎, 08-11-2016 01:04 PM
    • Replies: 5
    • Views: 403
    08-30-2016, 04:01 PM Go to last post
  26. Positive predictive value of biased data

    Hey, I am currently dealing with prediction of binary data due to structural alerts. This means if a substructure is within the query structure it...

    Started by lilchaos‎, 08-29-2016 03:03 AM
    • Replies: 2
    • Views: 182
    08-30-2016, 01:21 AM Go to last post
  27. Matched Groups Statistics

    Hello all hope this is the right thread for the question and that someone will be able to help me out :confused: I have created a propensity...

    Started by summit cross‎, 08-29-2016 03:21 AM
    matched, matched controls, propensity score matching, regression analysis
    • Replies: 2
    • Views: 178
    08-29-2016, 01:42 PM Go to last post
  28. I need advice on Fisher's exact test

    I recently submitted a paper and in my study, I wanted to see if there is an association between a gene mutation and the absence/presence of the...

    Started by Coral‎, 08-25-2016 03:58 AM
    • Replies: 4
    • Views: 291
    08-29-2016, 03:50 AM Go to last post
  29. calculate p value significance

    How to calculate p value significance for the following? We educated 334 individuals over the age of 50 about cancer. 87 (26.05%) of them made...

    Started by deepbiomed‎, 08-26-2016 11:24 AM
    #cancer #education effect
    • Replies: 2
    • Views: 262
    08-27-2016, 06:48 AM Go to last post
  30. Help on Bhapkar's Test using SAS/R/SPSS?

    Hi All, I am currently wandering in the unfamiliar territory of the Bhapkar's test, and hopefully someone can provide some guidance... Please see...

    Started by lennexyu‎, 08-19-2016 01:24 AM
    • Replies: 3
    • Views: 398
    08-22-2016, 09:47 PM Go to last post
  31. Help with statistical power?

    Hi, I'm doing a study looking at the ability of a test to detect a change in bacterial numbers pre- versus post-treatment . I've done a chi-square...

    Started by mgzx‎, 08-20-2016 10:42 PM
    chi-square, power, sample size, significance
    • Replies: 2
    • Views: 218
    08-21-2016, 03:01 AM Go to last post
  32. Graphpad or SPSS way to analyze this question

    Dear friends, I have ~3500 patients. I have ages for everyone of them, and i have a laboratory value for each one as well. I want to know if the...

    Started by docoftheworld‎, 08-15-2016 10:14 AM
    • Replies: 4
    • Views: 269
    08-15-2016, 08:48 PM Go to last post
  33. some urgent help

    dear all I'm in need for the solution of chapter 7 ,8 and 9 of the book (Fundamentals of Biostatistics S e v e n t h E d i t i o n Bernard...

    Started by dafer‎, 08-15-2016 05:42 AM
    • Replies: 1
    • Views: 189
    08-15-2016, 08:46 AM Go to last post
  34. Fisher Test for 5x2 table with SAS or R

    Hi, I wish to perform a Fisher Test for a 5x2 contingency table. I have a patient population divided in to 5 treatment groups, each with a...

    Started by BioStatNoob‎, 08-12-2016 07:43 AM
    • Replies: 3
    • Views: 246
    08-13-2016, 11:38 PM Go to last post
  35. How to obtain an unbiased post-stratified estimator for survival probabilities?

    Suppose I have estimated the survival probabilities $\hat{S(t)}_1, \hat{S(t)}_2, \ldots, \hat{S(t)}_H$ from $H$ strata. Now I want to get an unbiased...

    Started by Blain Waan‎, 08-12-2016 08:14 PM
    estimator, stratification, survival
    • Replies: 1
    • Views: 226
    08-13-2016, 09:24 AM Go to last post
  36. Repeated Measures Analysis with a long baseline period

    I am currently attempting to analyze the efficacy of a treatment on a premature baby's SpO2 levels. I have many measurements before the treatment...

    Started by Nives_ES‎, 08-08-2016 10:41 AM
    • Replies: 0
    • Views: 225
    08-08-2016, 10:41 AM Go to last post
  37. Mean and SD of two means and SD

    If we have two groups of males, group 1: age >60 and group 2 <60. each of these groups have mean and SD; can we calculate a mean and SD for all...

    Started by docoftheworld‎, 08-02-2016 10:08 AM
    • Replies: 13
    • Views: 598
    08-04-2016, 11:36 PM Go to last post
  38. Beginner questions: Clinical trial

    Hi there! I am a medical student working on my PhD, and I am analyzing some data for a meeting. Since we don't learn much about statistics (at...

    Started by Queen_in_the_North‎, 08-03-2016 02:37 PM
    beginner, correlation, pspp, significance, t-test
    • Replies: 0
    • Views: 213
    08-03-2016, 02:37 PM Go to last post
  39. Interpreting odds ratio in ordinal logistic regression

    Hi All, My data is from an educational programme for students. Questionnaire data was collected pre-intervention and post-intervention. We are...

    Started by lennexyu‎, 08-01-2016 08:54 PM
    • Replies: 2
    • Views: 291
    08-03-2016, 01:31 AM Go to last post
  40. Question Is this the right away to perform a trend analysis in a r*c table?

    I might be not posting the question in the right forum since I didn't get any advice so far (after 20 viewers) and my project is a public health one,...

    Started by belindalimm‎, 07-29-2016 04:19 PM
    • Replies: 1
    • Views: 263
    08-01-2016, 01:01 PM Go to last post
  41. Intrarater reliability for continuous variable

    I was hopeful for some advice on how to assess intrarater (not inter) reliability. My specific problem is 1 rater repeats a measurement on 20...

    Started by viostorm‎, 07-30-2016 11:25 AM
    • Replies: 2
    • Views: 288
    07-30-2016, 12:22 PM Go to last post
  42. SAS Coding to find averages for every 60 observations

    Hi. I am working on an analysis for research on premature baby health. I ran into a SAS coding issue which I hope some of you can help me with. ...

    Started by Nives_ES‎, 07-28-2016 10:26 AM
    sas mean research coding
    • Replies: 10
    • Views: 385
    07-29-2016, 01:38 PM Go to last post
  43. Paired or Unpaired T-test?

    If I have traps set to capture a certain animal at night vs. during the day, would I use a paired or unpaired T-test? I'd be comparing the mean...

    Started by OMai‎, 05-22-2016 10:59 AM
    paired, t-test, unpaired
    • Replies: 3
    • Views: 412
    07-28-2016, 03:22 PM Go to last post
  44. Cox's regression

    Hello, I have some experimental data for animals with tumours. Unfortunately, they were not followed individually during a time course, but...

    Started by confused1‎, 07-27-2016 06:03 AM
    biostatistics, cancer, cox, regression, survival
    • Replies: 0
    • Views: 349
    07-27-2016, 06:03 AM Go to last post
  45. starting in biostats and need to analyse clinical data. how to begin.

    Hello everybody I am a very beginer in stats and in using SPSS. I need to analyse some clinical data. I want to know please if this is a good...

    Started by Stat_begi‎, 07-22-2016 02:21 PM
    • Replies: 1
    • Views: 390
    07-22-2016, 03:54 PM Go to last post
  46. Which statistical approach?

    Dear all, I am a biologist with a very poor statistical knowledge so please excuse me if my question is not very well formulated- I am doing my best...

    Started by Nessie‎, 07-18-2016 08:57 AM
    gene related
    • Replies: 4
    • Views: 448
    07-18-2016, 09:41 AM Go to last post
  47. Correct analysis of crossover trials

    Hi everybody I was wondering if anyone here had any expertise regarding analysis of crossover trials. I'm writing my thesis at the moment and...

    Started by TNK78‎, 07-18-2016 06:56 AM
    analysis, crossover trial, treatment sequence
    • Replies: 1
    • Views: 206
    07-18-2016, 08:29 AM Go to last post
  48. Author's interpretation of Odds Ratio and Confidence intervals

    Hi all, Having some difficulty understanding the results of this paper I am including in a review. It compares the effects of 3 interventions...

    Started by crkc‎, 07-16-2016 07:23 AM
    confidence interval, intervention, odds ratio, significance
    • Replies: 1
    • Views: 241
    07-16-2016, 08:16 AM Go to last post
  49. What does a mean probability mean?

    Hi all. If each case in a dataset is assigned a probability of a certain event having occurred (based on their own individual data) and I...

    Started by blue11‎, 07-13-2016 06:09 PM
    • Replies: 1
    • Views: 292
    07-13-2016, 07:05 PM Go to last post
  50. Computing age and gender standardised mean BMI

    Hi, I'll appreciate a lot if someone could tell me how to compute age and gender standardised mean BMI in stata. Thanks. ZZ

    Started by Zain Zaid‎, 07-10-2016 08:20 PM
    • Replies: 0
    • Views: 371
    07-10-2016, 08:20 PM Go to last post
  51. Please help interpret cross-sectional study results (odds ratio, relevant risk, etc.)

    I'm trying to help my wife with some statistics. She's looking to see if people with Removable Dentures (RD) have a higher prevalence of Combination...

    Started by jbbuck‎, 07-08-2016 04:32 PM
    confidence interval, cross-sectional study, odds ratio, relative risk
    • Replies: 1
    • Views: 301
    07-09-2016, 03:35 AM Go to last post
  52. Lightbulb power calculation for two groups (parallel)

    Hi I have got 400 and 600 samples in control and test groups respectively. And in each of these two groups, i have an effect variable that occurs at...

    Started by rony443‎, 07-08-2016 02:01 AM
    power analysis, sample size
    • Replies: 2
    • Views: 262
    07-08-2016, 10:54 AM Go to last post
  53. SPSS, descriptive statistics, crosstabs, risk

    the problem has been solved. thanks

    Started by Menekse‎, 07-07-2016 03:36 AM
    • Replies: 0
    • Views: 230
    07-07-2016, 03:36 AM Go to last post
  54. Parallel Bioequivalence Study Sample Size

    I need to calculate the required sample size given the following information: Power=80% Coefficient of variation for Cmax and AUC = 40% True...

    Started by gopher‎, 07-04-2016 03:26 AM
    bioequivalence, sample size calculation
    • Replies: 0
    • Views: 315
    07-04-2016, 03:26 AM Go to last post
  55. Question How to prove two methods are “similar”?

    We are testing two imaging machines. One of the machines has been validated numerous times. However, we built the new machine and we need to prove...

    Started by yolo123‎, 07-01-2016 09:40 AM
    physics, research, statistics, validation
    • Replies: 1
    • Views: 411
    07-01-2016, 10:40 AM Go to last post
  56. External Validation of Cox Model

    I have two data set (training and validation) for building and validating a Cox model. With the training data set I fitted a cox model using...

    Started by Jyde‎, 06-28-2016 05:17 AM
    cox proportional hazard, sas clinical, survival analysis, validation
    • Replies: 8
    • Views: 558
    06-29-2016, 04:18 AM Go to last post
  57. Help interpreting an interaction in Binary Logistic Regression

    Firstly, thank you for taking the time to read my problem that I am having. The goal: interpret the direction of the interaction term. ...

    Started by 2+2=5‎, 06-25-2016 09:50 AM
    interaction effect, logisitic regression, logistic interaction
    • Replies: 3
    • Views: 401
    06-25-2016, 04:05 PM Go to last post
  58. Calculating standard deviation from mean and P value

    I am doing a systematic review and one of the papers I am including has reported the data only as mean, sample size and P value. I need the mean and...

    Started by CMP‎, 06-22-2016 03:35 PM
    • Replies: 10
    • Views: 642
    06-24-2016, 10:10 AM Go to last post
  59. Permutation correlation with one non-normal variable

    Hi, I am trying to assess the relationship between a relatively normally distributed variable (brain volume) and a strongly right-skewed...

    Started by nielsl‎, 06-23-2016 03:06 AM
    correlation, pearson, permutation
    • Replies: 1
    • Views: 270
    06-24-2016, 02:45 AM Go to last post
  60. Computing effect size with adverse event counts?

    Hello! I'm working on a meta-analysis, and I have a special problem regarding effect size. Can anyone lend me some insight? I have a treatment...

    Started by wag‎, 03-14-2016 02:26 PM
    • Replies: 1
    • Views: 475
    06-22-2016, 05:34 PM Go to last post

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