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Forum: Biostatistics

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

  1. 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, Yesterday 11:22 AM
    • Replies: 0
    • Views: 53
    Yesterday, 11:22 AM Go to last post
  2. 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, Yesterday 09:47 AM
    • Replies: 0
    • Views: 51
    Yesterday, 09:47 AM Go to last post
  3. 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, Yesterday 03:37 AM
    • Replies: 0
    • Views: 57
    Yesterday, 03:37 AM Go to last post
  4. 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: 91
    04-24-2015, 07:44 AM Go to last post
  5. 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: 92
    04-22-2015, 11:21 AM Go to last post
  6. 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: 212
    04-17-2015, 03:44 PM Go to last post
  7. 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: 191
    04-15-2015, 11:52 AM Go to last post
  8. 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: 192
    04-12-2015, 08:53 PM Go to last post
  9. 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: 132
    04-12-2015, 04:29 PM Go to last post
  10. 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: 147
    04-11-2015, 10:13 AM Go to last post
  11. 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: 138
    04-10-2015, 11:28 AM Go to last post
  12. 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: 213
    04-09-2015, 01:34 PM Go to last post
  13. 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: 193
    04-09-2015, 11:45 AM Go to last post
  14. 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: 196
    04-08-2015, 01:58 PM Go to last post
  15. 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: 261
    04-07-2015, 10:29 PM Go to last post
  16. 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: 364
    04-07-2015, 10:12 AM Go to last post
  17. 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: 161
    04-05-2015, 11:13 AM Go to last post
  18. 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: 415
    04-02-2015, 12:36 PM Go to last post
  19. 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: 97
    04-02-2015, 08:57 AM Go to last post
  20. 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: 276
    04-01-2015, 01:04 PM Go to last post
  21. 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: 324
    03-27-2015, 09:48 PM Go to last post
  22. 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: 330
    03-27-2015, 11:32 AM Go to last post
  23. 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: 156
    03-26-2015, 06:20 AM Go to last post
  24. 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: 327
    03-25-2015, 07:33 AM Go to last post
  25. 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: 155
    03-24-2015, 10:10 AM Go to last post
  26. 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: 327
    03-23-2015, 11:10 AM Go to last post
  27. 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: 230
    03-23-2015, 09:22 AM Go to last post
  28. 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: 390
    03-23-2015, 08:56 AM Go to last post
  29. 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: 199
    03-20-2015, 01:35 AM Go to last post
  30. 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: 265
    03-17-2015, 06:45 AM Go to last post
  31. 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: 189
    03-16-2015, 08:55 PM Go to last post
  32. 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: 247
    03-16-2015, 07:49 PM Go to last post
  33. 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: 279
    03-16-2015, 03:18 AM Go to last post
  34. 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: 265
    03-14-2015, 02:20 PM Go to last post
  35. 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: 203
    03-13-2015, 10:31 PM Go to last post
  36. 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: 221
    03-12-2015, 12:09 PM Go to last post
  37. 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: 316
    03-12-2015, 06:25 AM Go to last post
  38. 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: 252
    03-10-2015, 02:30 PM Go to last post
  39. 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: 157
    03-10-2015, 11:56 AM Go to last post
  40. 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: 332
    03-06-2015, 07:44 AM Go to last post
  41. 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: 181
    03-05-2015, 10:51 AM Go to last post
  42. Is the Cox Model correct in this case?

    Dear all, thanks for the help in advance, this is my issue: I am studying whether skipping a scheduled medical examination (which is every 4 weeks...

    Started by Ralph84‎, 03-04-2015 12:27 PM
    • Replies: 1
    • Views: 205
    03-05-2015, 09:02 AM Go to last post
  43. Survival curve from competing risk analysis

    I conducted a competing risk analysis of time-to-event data and produced graphs for the cumulative incidence functions. The investigator that I am...

    Started by mostater‎, 03-04-2015 09:07 AM
    • Replies: 2
    • Views: 165
    03-05-2015, 08:48 AM Go to last post
  44. Linear Mixed Model Analysis with multiple fixed factors

    Hellow, Here is a question on linear mixed model analysis for an intervention The study composed of two group of subjects who receive a DrugA...

    Started by risu‎, 02-20-2015 05:09 AM
    • Replies: 4
    • Views: 335
    03-05-2015, 08:02 AM Go to last post
  45. How to calculate the confidence interval of the ratio of two means (paired data)

    Hi there, I am writing a systematic review and need to calculate the 95% confidence intervals of the ratio of means from whatever the clinical...

    Started by FitzChivalry‎, 02-18-2015 04:17 PM
    confidence intervals, paired data, ratio of means
    • Replies: 7
    • Views: 479
    03-05-2015, 12:32 AM Go to last post
  46. Regression vs. t-test

    Hello all, I have this small study, and I am wondering how to analyze it. I have a measure X taken before some event, and after for every...

    Started by Yankel‎, 03-04-2015 04:52 AM
    • Replies: 6
    • Views: 287
    03-04-2015, 01:53 PM Go to last post
  47. Question Need help

    I have 3 groups, out of these 3, 1 is the control group. other two i have studied the effect of two modes of exercise. so i have before and after...

    Started by pavithran‎, 02-27-2015 09:25 AM
    • Replies: 2
    • Views: 341
    03-04-2015, 11:28 AM Go to last post
  48. Case control study - selection of control group

    I am starting a nested case control study using a pre existing dataset. I want to look at patient factors associated with relapse of tuberculosis. I...

    Started by andros23‎, 01-07-2015 10:12 AM
    case control; matched, stata commands
    • Replies: 5
    • Views: 490
    03-02-2015, 10:08 AM Go to last post
  49. comparing two dose(inhibition) respose curves log vs log log

    I'm not a stats person, so I need some help. I am looking for a statistics model to compare one dose(inhibition) response curve to the log space...

    Started by BrainExploding‎, 02-27-2015 03:52 PM
    • Replies: 0
    • Views: 200
    02-27-2015, 03:52 PM Go to last post
  50. Clustering sites to compare with cluster of species similarity (dendrogram?)

    Hi, I hope someone can help me here. I kind of have something specific in mind to analyze parts of my data, but I am not sure how to get there. I...

    Started by Aquaziell‎, 02-20-2015 09:35 AM
    • Replies: 2
    • Views: 283
    02-27-2015, 12:06 PM Go to last post
  51. Calculating life expectancy for cancer patients

    Hi all I have been asked to use life table analysis to calculate life expectancy for cancer patients from birth. I am comparing 3 different...

    Started by Suze‎, 02-26-2015 02:56 AM
    life expectancy, survival analysis
    • Replies: 0
    • Views: 178
    02-26-2015, 02:56 AM Go to last post
  52. How to calculate the covariance of two paired, continuous measurements

    Hi there, Is it possible to calculate the covariance of two paired, continuous measurements in a before-after clinical trial design without the...

    Started by FitzChivalry‎, 02-25-2015 10:43 PM
    • Replies: 0
    • Views: 187
    02-25-2015, 10:43 PM Go to last post
  53. Retrospective review analysis questions

    Hello! I am new to this forum. Thank you in advance for any help you can give!:wave: I am doing a prelim analysis for a pilot study I have...

    Started by boomer‎, 02-25-2015 09:57 AM
    • Replies: 3
    • Views: 268
    02-25-2015, 04:46 PM Go to last post
  54. outcomes of surgery

    Can someone point me into the right direction I have a database of patients who have had surgery which is deemed a success or not(0,1). Each...

    Started by edmundfitz‎, 02-23-2015 04:32 PM
    logistic regression
    • Replies: 3
    • Views: 298
    02-24-2015, 02:47 PM Go to last post
  55. Chi square vs Mcneamar's test

    Hello I have a cohort study where a cohort of subjects with a specific characteristic has been matched to a control group according to age (+/ 3...

    Started by Ralph84‎, 02-14-2015 08:56 AM
    • Replies: 3
    • Views: 396
    02-23-2015, 10:43 AM Go to last post
  56. [R] Non-parametric test to multi factorial ANOVA

    Hi, I've spent hours searching online (by "non parametric factorial ANOVA"), reading in books (Zar's "Biostatistical analysis") and manuals (R),...

    Started by Saccharo‎, 02-19-2015 05:52 PM
    • Replies: 3
    • Views: 398
    02-23-2015, 09:19 AM Go to last post
  57. Formula for S shaped curve given specific values

    I need to derive a formula that will give me an S-shaped curve, such as this one: The x-values would go from 0 to 250 and the y-values from 0 to...

    Started by Sharidb‎, 02-19-2015 04:54 AM
    gompertz, logistic
    • Replies: 3
    • Views: 304
    02-19-2015, 12:52 PM Go to last post
  58. Pearson's versus Spearman's correlation

    I am trying to determine which correlation coefficient is more appropriate. The two variables to be correlated are visual acuity (which can be...

    Started by jle‎, 02-11-2015 06:54 PM
    • Replies: 6
    • Views: 527
    02-13-2015, 04:59 PM Go to last post
  59. Sample size calculation in clinical trial

    Could you please help me understand how did they calculate the sample size in this randomized trial ? It is a randomized trial comparing the use...

    Started by goodfella‎, 02-12-2015 10:29 AM
    • Replies: 0
    • Views: 233
    02-12-2015, 10:29 AM Go to last post
  60. Cmax as covariate in mixed model?

    Hello, I am involved in a study looking at drug effects on HR. We have one treatment and one placebo group, and are testing patients once/week for 8...

    Started by jcr‎, 02-11-2015 09:08 PM
    • Replies: 0
    • Views: 180
    02-11-2015, 09:08 PM Go to last post

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