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Forum: Biostatistics

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

  1. 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: 232
    08-22-2016, 09:47 PM Go to last post
  2. 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: 121
    08-21-2016, 03:01 AM Go to last post
  3. 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: 187
    08-15-2016, 08:48 PM Go to last post
  4. 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: 97
    08-15-2016, 08:46 AM Go to last post
  5. 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: 149
    08-13-2016, 11:38 PM Go to last post
  6. 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: 136
    08-13-2016, 09:24 AM Go to last post
  7. 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: 1
    • Views: 128
    08-11-2016, 04:05 PM Go to last post
  8. 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: 149
    08-08-2016, 10:41 AM Go to last post
  9. 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: 417
    08-04-2016, 11:36 PM Go to last post
  10. 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: 114
    08-03-2016, 02:37 PM Go to last post
  11. 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: 184
    08-03-2016, 01:31 AM Go to last post
  12. 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: 165
    08-01-2016, 01:01 PM Go to last post
  13. 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: 189
    07-30-2016, 12:22 PM Go to last post
  14. 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: 255
    07-29-2016, 01:38 PM Go to last post
  15. 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: 297
    07-28-2016, 03:22 PM Go to last post
  16. 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: 182
    07-27-2016, 06:03 AM Go to last post
  17. 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: 255
    07-22-2016, 03:54 PM Go to last post
  18. 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: 349
    07-18-2016, 09:41 AM Go to last post
  19. 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: 131
    07-18-2016, 08:29 AM Go to last post
  20. 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: 168
    07-16-2016, 08:16 AM Go to last post
  21. 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: 206
    07-13-2016, 07:05 PM Go to last post
  22. 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: 305
    07-10-2016, 08:20 PM Go to last post
  23. 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: 232
    07-09-2016, 03:35 AM Go to last post
  24. 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: 193
    07-08-2016, 10:54 AM Go to last post
  25. SPSS, descriptive statistics, crosstabs, risk

    the problem has been solved. thanks

    Started by Menekse‎, 07-07-2016 03:36 AM
    • Replies: 0
    • Views: 167
    07-07-2016, 03:36 AM Go to last post
  26. 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: 255
    07-04-2016, 03:26 AM Go to last post
  27. 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: 293
    07-01-2016, 10:40 AM Go to last post
  28. 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: 466
    06-29-2016, 04:18 AM Go to last post
  29. 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: 318
    06-25-2016, 04:05 PM Go to last post
  30. 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: 525
    06-24-2016, 10:10 AM Go to last post
  31. 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: 216
    06-24-2016, 02:45 AM Go to last post
  32. 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: 412
    06-22-2016, 05:34 PM Go to last post
  33. Triple crossover study and multivariate model with paired data

    Hi, I would like to analyze data from a triple crossover study. Same population received same drug (or placebo) three times a day with...

    Started by Markica85‎, 05-28-2016 03:51 AM
    • Replies: 1
    • Views: 359
    06-21-2016, 06:50 AM Go to last post
  34. Question Statistical Approach for data (uneven intervals)

    Hello, What statistical approach would you recommend for a data of the following pattern. In a 12-hour window, each row/ID is an independent...

    Started by rvr‎, 06-20-2016 12:23 PM
    frequency distribution, model selection, statistical approach, time interval, uneven tests taken
    • Replies: 0
    • Views: 212
    06-20-2016, 12:23 PM Go to last post
  35. Test for ordinal DV in mixed design

    What's the corresponding test to Two way Mixed ANOVA when the DV is ordinal? I have two treatment groups, 14 time points and the DV is an ordinal...

    Started by Logician‎, 06-14-2016 06:55 PM
    • Replies: 0
    • Views: 543
    06-14-2016, 06:55 PM Go to last post
  36. How to construct a scatter graph with percentiles lines

    Good day, How to construct a scatter graph with percentiles lines, like the one in the image below, with any program ?

    Started by tonia bird‎, 06-04-2016 01:35 PM
    • Replies: 3
    • Views: 571
    06-11-2016, 06:13 PM Go to last post
  37. Repeatability and Logistic Regression?

    Hi all, my stats knowledge is quite basic so I would appreciate any help you can provide! I am working on a study looking at inter-grader and...

    Started by StatsN00bie‎, 06-10-2016 01:04 PM
    • Replies: 2
    • Views: 319
    06-10-2016, 02:02 PM Go to last post
  38. Is this study a case-control or retrospective cohort?

    "Recently we retrospectively examined the spine on pyelograms of 34 children with Wilms tumour. The findings were compared with those obtained in 148...

    Started by klionj‎, 06-02-2016 11:44 PM
    • Replies: 0
    • Views: 282
    06-02-2016, 11:44 PM Go to last post
  39. Significance of a Dichotomous Variable Over a Continuous Variable

    Hi all! I ran an analysis using the 2005 healthy eating index (HEI) score as the dependent variable and am a bit confused by my results. The HEI...

    Started by tnrose87‎, 05-31-2016 07:12 PM
    • Replies: 1
    • Views: 276
    06-01-2016, 06:24 AM Go to last post
  40. Chi Square for Molecular Screening Comparison

    Hi, I'm trying to run a chi square test to compare two different screening methods for a pathogen. I'm testing this by diluting a known positive...

    Started by OMai‎, 05-31-2016 03:59 PM
    • Replies: 0
    • Views: 163
    05-31-2016, 03:59 PM Go to last post
  41. Best Statistical test for data

    Hi All, Just wondering if someone could help with an issue with my data. I am wanting to analyse the relationship between continuous variable...

    Started by HRS‎, 05-25-2016 03:48 AM
    • Replies: 3
    • Views: 387
    05-26-2016, 06:49 AM Go to last post
  42. ANCOVA assmptions not met.

    Hi, What is the non parametric alternative for parametric ANCOVA if we find that some ANCOVA assumptions are not met? How it can be done in SAS?

    Started by shruti verma‎, 05-25-2016 03:46 AM
    analysis, analysis of covariance, ancova, assumptions
    • Replies: 1
    • Views: 191
    05-25-2016, 04:03 AM Go to last post
  43. Score methods

    Hello everyone, I would like your opinion. my data is score (before and after therapy) on radiographs made with x-ray instrument and score based on...

    Started by andrew_fg‎, 05-23-2016 01:47 PM
    • Replies: 2
    • Views: 259
    05-24-2016, 01:55 PM Go to last post
  44. Please help me selecting a test for my study

    Hi, I was wondering if you guys can provide some ideas on best test for my samples size, since I am not very stat savvy. My project consist of...

    Started by kite6k‎, 05-18-2016 12:07 PM
    • Replies: 4
    • Views: 333
    05-24-2016, 09:03 AM Go to last post
  45. Frequency analysis

    Hello. I have a problem with my analysis. I got 2 groups which take drug (Group 1 (50 people) takes real medicine and Group 2 (40 people) takes...

    Started by Makina‎, 05-20-2016 04:50 AM
    • Replies: 7
    • Views: 448
    05-23-2016, 08:12 AM Go to last post
  46. Non parametric multivariate analysis. maybe :(

    Hello to everyone, i need some help with my statistical analysis. I have two different pharmacokinetic parameters. They result from two different...

    Started by bluina‎, 05-11-2016 03:38 AM
    biostatistics, multivariate analysis, non parametric
    • Replies: 4
    • Views: 408
    05-20-2016, 04:07 AM Go to last post
  47. Which statistical test shoud I use?

    I have concentrations of one metal in two organs of a snail – kidney and foot (n=10). What statistical test should I use to check if the difference...

    Started by Miii‎, 05-19-2016 06:36 AM
    • Replies: 7
    • Views: 358
    05-19-2016, 02:27 PM Go to last post
  48. LD50 and ED50 calculation with Probit and other methods

    hello All i'm not have good experiences in bio-statistic and want to know how can i calculate LD50 for Bacteria and ED50 for Bacterial Vaccine...

    Started by mazan2010‎, 05-18-2016 01:19 PM
    • Replies: 0
    • Views: 236
    05-18-2016, 01:19 PM Go to last post
  49. Integrate different types of data from different studies?

    Hi, Is it possible to integrate different types of data from different studies? If yes, what precautions we must take? For example, let us...

    Started by GN1‎, 05-17-2016 01:43 AM
    biostatistics, research article
    • Replies: 1
    • Views: 249
    05-18-2016, 08:26 AM Go to last post
  50. Metal accumulation dependence on weight and pollution

    I'm working on metal accumulation in two landsnail species and it includes their kidneys and feet. I have concentrations of 7 metals in these organs...

    Started by Miii‎, 05-18-2016 04:42 AM
    • Replies: 1
    • Views: 280
    05-18-2016, 07:26 AM Go to last post
  51. I do not know how to calculate my sample size…

    Hello, can someone help me calculate my sample size and showing me the steps of how it should be done? I am going to do a study to see a...

    Started by Maria voltaren‎, 05-16-2016 04:37 AM
    sample size calculation
    • Replies: 0
    • Views: 270
    05-16-2016, 04:37 AM Go to last post
  52. Query about RRs and confounders

    Hi I am doing my head in over something very simple. Its more theoretical and I'm trying to work out a method. I am hoping someone can clarify...

    Started by statsanon‎, 05-15-2016 07:02 PM
    • Replies: 0
    • Views: 205
    05-15-2016, 07:02 PM Go to last post
  53. Question Safety or efficacy outcome?

    Dear friends, I got confused regarding outcome study I had to review. The primary outcome is: Time to the first occurrence of any of the...

    Started by wellfor‎, 05-14-2016 12:47 PM
    efficacy, outcome, safety
    • Replies: 0
    • Views: 246
    05-14-2016, 12:47 PM Go to last post
  54. Statistical test for proportions (values' range: 0-1)

    I am trying to compare mass spec data from 3 different conditions. For each protein I detected in my samples I have 3 values/condition (from 3...

    Started by jalbertortega‎, 05-13-2016 12:54 PM
    • Replies: 1
    • Views: 268
    05-14-2016, 09:10 AM Go to last post
  55. chi-square test

    Hi, can somone help me with doing a Chi-square test or Yates corrected chi-square test of the data file attached. I dont get it, or is the test...

    Started by Anne3‎, 05-12-2016 07:33 AM
    • Replies: 0
    • Views: 319
    05-12-2016, 07:33 AM Go to last post
  56. Problems in Cox proportional hazards model, Survival analysis.

    Hello everyone, I got trouble with some problems as following Suppose a Cox proportional hazards model was fit with 2 covariates, smoking status...

    Started by Leon Yo‎, 04-24-2016 12:39 PM
    • Replies: 1
    • Views: 281
    05-11-2016, 12:33 AM Go to last post
  57. Repeated measures with one between subject and two within subject factors

    I have measured plasma cortisol levels in blood samples collected at an interval of 1 hour over a period of 24 hours in 10 male and female animals...

    Started by Bharath‎, 05-02-2016 06:05 PM
    • Replies: 2
    • Views: 381
    05-08-2016, 08:27 PM Go to last post
  58. Bootstrap strange estimate

    Hello everyone, I'm a statistical novice, I would like your help. I'm analyzing non-normally distributed variables. To develop the confidence...

    Started by andrew_fg‎, 05-06-2016 12:52 PM
    • Replies: 5
    • Views: 380
    05-06-2016, 06:40 PM Go to last post
  59. Best way to calculate power, precision & sample size using complex pilot data set?

    I have a large and complex pilot data set of electromyographic (EMG) data collected from human subjects performing several different exercises. A...

    Started by statsSeeker‎, 04-29-2016 01:47 PM
    power, precision, sample size calculation, sample size determination
    • Replies: 2
    • Views: 357
    05-05-2016, 01:16 PM Go to last post
  60. should I include a table with non significant results of Z proportion tests

    I am writing a manuscript and have a table with ONLY non significant Z proportion test results. I am wondering whether to omit this table although it...

    Started by Moranke‎, 05-02-2016 03:34 AM
    • Replies: 1
    • Views: 237
    05-05-2016, 07:26 AM Go to last post

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