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Forum: Biostatistics

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

  1. PCA questions?

    Hi there, I am a bit new to statistics and have a few questions. I am currently doing my dissertation on the consistent and variable...

    Started by Callum94‎, Yesterday 12:59 PM
    • Replies: 3
    • Views: 147
    Yesterday, 06:36 PM Go to last post
  2. Predicting outcome with multiple groups

    Hi everyone, I'm currently working with 3 different groups (3 disease populations) and I would like to predict which of the three groups they fall...

    Started by Eric2014‎, 03-28-2017 12:14 PM
    groups, logistic, prediction, regression
    • Replies: 4
    • Views: 137
    03-28-2017, 03:45 PM Go to last post
  3. Finding data given sample mean and variance

    Hello, I have a problem, I am given the sample size, mean, variance, and I know it is normally distributed. The question states that 160...

    Started by dorothy8‎, 03-26-2017 06:56 PM
    • Replies: 2
    • Views: 156
    03-27-2017, 09:56 PM Go to last post
  4. am i overadjusting?

    might sound silly but for my research topic I am looking into insulin resistance (IR) and dietary factors. We are measuring IR by the use of...

    Started by jkerr1‎, 03-27-2017 04:56 AM
    • Replies: 1
    • Views: 117
    03-27-2017, 10:23 AM Go to last post
  5. Confidence interval question

    Fr a sample of 100 hypertensive patients, we find that a 95% confidence interval of systolic BP to be . What statement is FALSE? A- if a drug is...

    Started by dorothy8‎, 03-26-2017 05:53 PM
    • Replies: 1
    • Views: 112
    03-27-2017, 02:20 AM Go to last post
  6. Question reference interval determination

    Hi all, I was wondering if I could ask for some help from some more statistically inclined persons than myself. We are trying to determine a...

    Started by romes‎, 03-25-2017 10:23 AM
    biostatistics, reference interval
    • Replies: 0
    • Views: 98
    03-25-2017, 10:23 AM Go to last post
  7. Pre and post comparison for nonparametric unpaired sample

    Hi. I am not sure how to compare the results from the following study. Number of wrong orders out of total orders placed every day for 60 days as...

    Started by anupamsule‎, 03-22-2017 09:01 PM
    • Replies: 2
    • Views: 214
    03-24-2017, 07:04 AM Go to last post
  8. Dealing with Log(0)

    Dear all, Iíve been stuck for quite some time with a problem that relates to use of log-scale with values that equal zero. My data comes from an...

    Started by ritmaniac‎, 03-21-2017 07:21 AM
    anova, linear regression, logarithmic
    • Replies: 2
    • Views: 215
    03-21-2017, 04:22 PM Go to last post
  9. Sample size calculation for 1:2 matched case-control study

    Hi, I have a matched case-control study with 12 cases and two controls for each case. Evaluating our findings, I want to calculate what our sample...

    Started by teapot‎, 03-08-2017 01:22 PM
    • Replies: 7
    • Views: 545
    03-17-2017, 08:59 AM Go to last post
  10. stratified log-rank test and proportional hazards

    Does stratified log-rank test overcome problem of violation of proportional hazards? I encountered a randomized controlled study of a new drug...

    Started by Markica85‎, 03-16-2017 04:53 AM
    • Replies: 0
    • Views: 222
    03-16-2017, 04:53 AM Go to last post
  11. Regarding Maximum Percent different

    Dear all, Could you please explain what maximum percent different for continues vital DiaBP data. How to calculate this? Could you any one...

    Started by Statvijay‎, 03-14-2017 07:08 AM
    • Replies: 0
    • Views: 139
    03-14-2017, 07:08 AM Go to last post
  12. Survival Analysis - Time to utilization of medical services

    Hi all, I work in the medical field and Iím looking into using survival analysis calculate time to utilization of medical services, that is, once...

    Started by avbraga‎, 03-10-2017 03:35 PM
    • Replies: 6
    • Views: 264
    03-13-2017, 06:07 PM Go to last post
  13. vision in eyes at different times

    Hi everyone, New to the forum and am seeking a bit of guidance as to how to compare vision (visual acuity) between eyes. So I am trying to...

    Started by jksgoh‎, 03-11-2017 01:44 AM
    • Replies: 1
    • Views: 214
    03-13-2017, 02:42 PM Go to last post
  14. Which statistical tests are appropriate: Group means before and after treatment

    I am trying to find out what statistical tests to run on a set of aggregate data (no individual data) on 3 different groups, variables are summarized...

    Started by PamelaF‎, 03-07-2017 03:17 AM
    • Replies: 1
    • Views: 303
    03-09-2017, 03:31 PM Go to last post
  15. Adjustment for correlated data in meta-anlaysis

    Hi, I'm completing a systematic review and performing meta-anlaysis forest plots. The research question related to the finding of risk factors for...

    Started by Ainslie‎, 03-07-2017 11:47 PM
    adjustment, correlated data, meta-analysis
    • Replies: 2
    • Views: 253
    03-08-2017, 10:07 AM Go to last post
  16. standard deviation greater than variance, is this ok?

    I am putting together some audit results and it was suggested I present them as mean +/- SD. However there is a significant variance in the results....

    Started by Roundtoit‎, 03-07-2017 04:44 PM
    • Replies: 7
    • Views: 389
    03-08-2017, 03:23 AM Go to last post
  17. Comparing diagnostic tests - graphically demonstration

    Hi, This is very basic but really struggling to find the correct terminology to find out what I want to do. I have collected data on two methods...

    Started by k093‎, 03-07-2017 06:17 PM
    • Replies: 0
    • Views: 187
    03-07-2017, 06:17 PM Go to last post
  18. interpretation of a negative risk difference

    Hi, I am reviewing a cohort study and trying to make sense of the results. When considering mortality they presented their results as a risk...

    Started by Roundtoit‎, 03-05-2017 02:10 PM
    biostatistics, cohort study, risk difference
    • Replies: 1
    • Views: 246
    03-05-2017, 03:02 PM Go to last post
  19. Correct application of multiple testing methods in projects with several experiments

    Hi! I have a problem with evaluating how I should correct my alpha and conduct statistical texts when I have several different exeriments in the...

    Started by Szkeptik‎, 02-23-2017 03:32 AM
    anova, holm-bonferroni method, multiple testing
    • Replies: 1
    • Views: 280
    03-04-2017, 09:36 PM Go to last post
  20. Smile Comparative study

    Im doing comparative study of Kidney disease and Dermatoglyphics. There is a Continuous variable (ridge count) i am assessing Confounding factors is...

    Started by buddhikatbw‎, 03-03-2017 08:24 AM
    case control study
    • Replies: 2
    • Views: 239
    03-03-2017, 08:36 PM Go to last post
  21. matched pre-post survey analysis help

    I have matched pre-and post test data that evaluated our workshop participants using Likert-type items. Meaning, the same people were given the same...

    Started by hipstats‎, 02-28-2017 04:10 PM
    • Replies: 3
    • Views: 290
    03-03-2017, 07:52 AM Go to last post
  22. Test negative factors among correlated determinants

    Dear all, I am working on the obesity research. I found a molecule A that is negatively control the generation of adipocytes. I have a cohort of...

    Started by pinetop‎, 02-24-2017 11:05 PM
    correlation, negative, regression
    • Replies: 1
    • Views: 278
    03-02-2017, 12:41 PM Go to last post
  23. Cox regression to adjust for site effect in multicenter trial

    Hello All, Can stratified Cox regression be used to adjust for site effect in multicenter trials? Thank you in advance to all those who reply.

    Started by ineedhelpplease‎, 02-27-2017 09:44 PM
    • Replies: 3
    • Views: 421
    02-28-2017, 04:34 PM Go to last post
  24. Testing for trend

    I have following data that represent number of new patients with rare disease for subsequent 5 year time periods: 4, 3, 4, 2, 4, 2, 4, 6, 11 As I...

    Started by Markica85‎, 02-25-2017 08:25 AM
    • Replies: 12
    • Views: 691
    02-28-2017, 12:30 PM Go to last post
  25. Analysis of Repeated Measures Study with Unequal Time Between Measurements

    Hello Everyone, I have inherited the analysis of a study from a previous research student. I am having trouble determining what type of analysis...

    Started by rafreakijones‎, 02-10-2017 11:42 AM
    • Replies: 1
    • Views: 304
    02-24-2017, 08:56 PM Go to last post
  26. Statistical method to compare two experiments

    I have two data from biological experiment where two types of cells were measured. For each cell the data about composition of the membrane where...

    Started by magruc‎, 02-22-2017 03:23 AM
    • Replies: 1
    • Views: 276
    02-24-2017, 03:04 PM Go to last post
  27. Moran's I Spatial Autocorrelation. Interpreting results.

    I have carried out a Moran's I test on the residuals of a GLM model in the "ape" package in R which has returned the output below: Observed:...

    Started by avocadorose‎, 02-22-2017 01:16 PM
    glm, interpretation, spatial autocorrelation
    • Replies: 1
    • Views: 357
    02-23-2017, 05:40 AM Go to last post
  28. ADjusting for variables in regression model

    Dear all, I'm comparing two populations of oncologic patients that were treated with two different regimens in two different hospitals, group A of...

    Started by Markica85‎, 02-13-2017 05:43 AM
    • Replies: 6
    • Views: 618
    02-22-2017, 12:56 PM Go to last post
  29. Can I combine univariate and multivariate HR?

    Hi guys. I'm doing a meta-analysis of survival based on a blood marker, and not all the studies have provided a multivariate hazard ratio. Some have...

    Started by ngmowbray‎, 02-21-2017 06:38 AM
    medical statistics, meta analysis
    • Replies: 6
    • Views: 298
    02-21-2017, 08:08 PM Go to last post
  30. Categorical Variable with Repeated Data Points

    Hello, I have some data (continuous DV, nominal IV), that I would like to run an ANOVA or regression on. Strictly speaking, I have 3 levels, but...

    Started by StatsN00bie‎, 02-15-2017 02:22 PM
    • Replies: 1
    • Views: 377
    02-15-2017, 04:40 PM Go to last post
  31. Clinical decision interval

    Hi all, I have a question regarding clinical decision intervals (grey zone). We have developed a new screening test and we want to provide the...

    Started by Vbogaert‎, 02-08-2017 01:41 AM
    • Replies: 1
    • Views: 317
    02-13-2017, 07:24 AM Go to last post
  32. Assessing covariates to include in model

    Hi all, I have a couple of basic questions which would be great to get some help on I have a continuous outcome (brain volume: total and divided...

    Started by Alanine‎, 02-09-2017 09:47 AM
    • Replies: 2
    • Views: 302
    02-10-2017, 05:57 AM Go to last post
  33. Question [RNA-Seq] Sparse (discrete) p values with Cuffdiff

    Hello biostatisticians, I have run a very standard RNA-Seq protocol using TopHat - Cufflinks - Cuffmerge and Cuffdiff to measure differential gene...

    Started by FR_myologist‎, 02-08-2017 01:49 PM
    • Replies: 0
    • Views: 309
    02-08-2017, 01:49 PM Go to last post
  34. propensity matching and ITT for cohort study

    I am reviewing a cohort study that used a retrospective database to determine if treatment with hypothermia post cardiac arrest improves survival to...

    Started by Roundtoit‎, 02-06-2017 03:49 PM
    itt, propensity score matching, sensitivity analysis, survival analysis
    • Replies: 0
    • Views: 352
    02-06-2017, 03:49 PM Go to last post
  35. fixed vs mixed random effects model

    greetings, I am reviewing some meta-analysis and have a question regarding fixed vs random effects models. 2 reviews have used basically the same...

    Started by Roundtoit‎, 02-05-2017 07:12 PM
    • Replies: 4
    • Views: 420
    02-06-2017, 03:45 PM Go to last post
  36. Compensate for correlated observations

    Dear users I have an issue that I am not to solve alone and I am here to ask for your help. I work in the ophthalmology field and I have a group of...

    Started by rabiolo.alessandro‎, 01-30-2017 06:09 PM
    • Replies: 4
    • Views: 686
    02-01-2017, 02:28 PM Go to last post
  37. Proper analysis method for dataset involving multiple sessions

    I have a dataset that was collected over 5 discrete sessions, with each session collected on a different date. During each session, 10 human subjects...

    Started by statsSeeker‎, 01-31-2017 02:01 PM
    multiple sessions
    • Replies: 0
    • Views: 353
    01-31-2017, 02:01 PM Go to last post
  38. Ratio between control and treatment siginificantly different than 1

    I would like to know what kind of test I can use to verify my findings. In general I have a two group of people. One is a control group the other one...

    Started by Shaxi Liver‎, 01-26-2017 09:10 AM
    • Replies: 2
    • Views: 646
    01-27-2017, 03:43 PM Go to last post
  39. Equivalence test or non inferiority test for non parametric data using stata or spss

    I am doing a retrospective study about a new medical device, comparing it with an older device. the first group has 18 cases and the other group has...

    Started by drAmrBadawy‎, 01-25-2017 08:25 PM
    • Replies: 4
    • Views: 552
    01-25-2017, 11:08 PM Go to last post
  40. McNemar or Chi sqared test for case-control study

    Dear all, I'm facing a dilemma which test would be appropriate to compare frequency of a feature in two age, sex and...

    Started by Markica85‎, 01-20-2017 05:59 AM
    • Replies: 5
    • Views: 781
    01-25-2017, 01:57 PM Go to last post
  41. Issues with ANOVA and bounded variables (percentages)

    Hey all, Iím new here. I have an issue with a percentages and the use of ANOVA. But letís start from the beginning. I m a PhD Student and I study...

    Started by MoltenLight‎, 01-25-2017 10:40 AM
    • Replies: 0
    • Views: 342
    01-25-2017, 10:40 AM Go to last post
  42. How to combine more datasets

    Hi everyone, Iím quite sorry for this very ďbeginner questionĒ , but Iím stuck on it from several days. I got three experimental groups, four...

    Started by Lodeacca‎, 01-24-2017 05:39 AM
    • Replies: 1
    • Views: 373
    01-24-2017, 07:05 AM Go to last post
  43. Exclamation Evaluation of correlation trend

    I would like to ask you for help and advice regarding one comment I received during the peer-review process for manuscript I submitted. My colleagues...

    Started by mzmph‎, 01-21-2017 06:19 PM
    correlation analysis
    • Replies: 1
    • Views: 486
    01-22-2017, 06:43 PM Go to last post
  44. Clinical Trial Simulator - Your feedback is welcomed!

    Hi all I hope it's alright if I introduce my clinical trial simulator app here. It's free and you can use it online to simulate a trial, check it...

    Started by mzhKU‎, 01-15-2017 10:33 AM
    • Replies: 4
    • Views: 751
    01-22-2017, 09:40 AM Go to last post
  45. Shiny App - Forest Plots

    Hi I've created a shiny app a while back that will create forest plots based on user supplied data through (a) uploading a data file (b)...

    Started by jamesmartinn‎, 01-16-2017 08:06 AM
    • Replies: 0
    • Views: 557
    01-16-2017, 08:06 AM Go to last post
  46. correlation study - Is my sample size too small?

    Hi there! i'm a pediatrician working in the neonatal ward, and i've recently finished aquiring data about a study that i'm doing - i'm trying to...

    Started by galkim‎, 01-15-2017 03:39 AM
    • Replies: 4
    • Views: 634
    01-16-2017, 01:17 AM Go to last post
  47. Multilinear regression?

    Hi, all: I need help for my research. I would like to develop an analytical method to detect the toxin A metabolites in exposed human urine; I...

    Started by ybz12003‎, 01-14-2017 05:34 PM
    • Replies: 1
    • Views: 496
    01-15-2017, 06:05 AM Go to last post
  48. Power analysis with one and two variables?

    Hi gang, I am severely illiterate in stats and so am struggling with what would seem to be a very straightforward problem. My problem: We...

    Started by ablum‎, 01-04-2017 03:18 PM
    • Replies: 1
    • Views: 799
    01-11-2017, 03:50 PM Go to last post
  49. Question on Odds ratio

    Hi, I have a basic understanding of odds ratio. I can't figure out how to integrate the space S into my odds ratio equation. For the following...

    Started by MinieMe‎, 01-10-2017 12:13 PM
    biostatistics, odds ratio
    • Replies: 2
    • Views: 575
    01-10-2017, 01:38 PM Go to last post
  50. Post What statistical test to use for species abundance between wet and dry season?

    Sorry if this question is trivial, I have a collection of camera trap data of recorded species during the rainy season and the dry season. I am...

    Started by BondHR‎, 01-07-2017 09:24 PM
    abundance, camera trap data, rstats, species data, statistics
    • Replies: 5
    • Views: 819
    01-08-2017, 01:38 PM Go to last post
  51. Temporal Distribution of Death

    Dear all, I plan to conduct a study. The preliminary aim is to examine the temporal distribution of death of terminal cancer patients in hospice...

    Started by bestmic‎, 12-20-2016 05:40 AM
    • Replies: 10
    • Views: 1,268
    01-03-2017, 03:40 AM Go to last post
  52. Add AUCs

    I want to add Area Under the Curve (AUC) from multiple meta analyses. AUC for each Meta analysis is given. How can I add them together?

    Started by Michael_svm‎, 12-20-2016 04:24 AM
    area under the curve, auc, diagnostic, roc
    • Replies: 6
    • Views: 1,043
    12-23-2016, 07:08 AM Go to last post
  53. Patterns in DNA, seperating signal from noise -- outliers?

    Hello all, I'm looking at patterns in fragments of RNA. What I need to do is separate the signals from noise in Exons (small regions of DNA/RNA)....

    Started by James1984‎, 10-10-2015 05:30 PM
    • Replies: 2
    • Views: 1,195
    12-22-2016, 04:05 AM Go to last post
  54. t-test or z-test for two proportions?

    We did an intervention to reduce the frequency of use of a certain type of treatment and now I want to compare the data pre vs post intervention. ...

    Started by hurricanemb‎, 12-18-2016 02:28 PM
    proportions, t-test, z-test
    • Replies: 3
    • Views: 773
    12-19-2016, 10:01 AM Go to last post
  55. Red face Interpreting Odds Ratios... weird question

    Hi, I sort of have a weird question. I have a basic understanding of ORs, and can interpret them, but it's never been clear to me why we...

    Started by Ceci18‎, 12-14-2016 09:34 AM
    • Replies: 6
    • Views: 892
    12-16-2016, 10:37 AM Go to last post
  56. Area under Kaplan Meier curve

    There is one thing bothering me for some time: What does area under Kaplan-Meier survival curve actally represent? Is there a plausible way to...

    Started by Markica85‎, 12-10-2016 04:55 AM
    kaplan meier, survival analysis
    • Replies: 0
    • Views: 961
    12-10-2016, 04:55 AM Go to last post
  57. Pooling time points to perform a Fisher test?

    Hello, I am currently trying to analyse an experiment to assess if rats with cerebral malformations have a sensitivity deficit on one of their...

    Started by Fanny-‎, 12-07-2016 11:10 AM
    anova, chi-square, fisher test
    • Replies: 4
    • Views: 970
    12-09-2016, 02:58 AM Go to last post
  58. What kind of statistical test can be used for my data?

    It is my first post on this forum so please be gentle. If it is not a proper section I would appreciate if moderator moves the thread to the correct...

    Started by Shaxi Liver‎, 12-07-2016 10:56 AM
    • Replies: 1
    • Views: 668
    12-07-2016, 12:27 PM Go to last post
  59. 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: 3
    • Views: 1,117
    12-06-2016, 10:07 AM Go to last post
  60. Why not use Kaplan Meier?

    In the method described here http://dmkd.cs.vt.edu/papers/TKDE17.pdf R code implementation is provided ...

    Started by pablrodr‎, 12-02-2016 03:07 PM
    exponential distribution, kaplan meier, weibull distribution
    • Replies: 5
    • Views: 808
    12-03-2016, 08:56 AM Go to last post

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