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Forum: Biostatistics

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

  1. help- comparison of 2 groupes of categorical data‏

    Dear all, I may need your suggestion for a statistical question. Now I have 2 groupes of data, I wanna see if there are differences in the...

    Started by lilylily‎, 02-10-2011 10:07 AM
    • Replies: 6
    • Views: 239,258
    02-15-2011, 10:28 AM Go to last post
  2. Non-parametric alternative to repeated-measures ANOVA with a between-subjects factor?

    Hello, I'm trying to do a repeated-measures ANOVA but my data is likely violating the multivariate normality assumption. My question is: Does...

    Started by PHO_M‎, 08-15-2012 04:19 PM
    • Replies: 4
    • Views: 60,517
    08-17-2012, 07:50 AM Go to last post
  3. p value of 0.000 on SPSS

    I am using SPSS to define relationship between two variables. Previous research has indicated a significant relationship between them. Spearman...

    Started by viciousorphan‎, 03-10-2013 01:13 AM
    • Replies: 6
    • Views: 58,930
    03-10-2013, 03:16 PM Go to last post
  4. •Comparing groups - which test should I use(t-test or ANOVA)

    The general infomation is: We have 6 kinds of material and have 4 group for each material now(please see the attached table) we cut one tooth to...

    Started by xiaohui‎, 02-23-2013 06:07 AM
    • Replies: 6
    • Views: 46,083
    03-17-2013, 05:43 AM Go to last post
  5. Comparing signal amplitude across multiple timepoints– what method should I use?

    Hi there, I am working on a research project looking at the effect of mood on brain response during visual perception. 20 volunteers participated...

    Started by panichem‎, 03-30-2012 03:25 PM
    • Replies: 4
    • Views: 44,656
    04-26-2012, 11:00 AM Go to last post
  6. Sample Size for Chi Square test

    Hello, I need to calculate a minimum sample size for the chi square test. I have two groups, sick and healthy patients, and I have a new test...

    Started by NN_STAT‎, 01-04-2012 02:38 AM
    • Replies: 7
    • Views: 39,030
    01-05-2012, 06:49 AM Go to last post
  7. Odds ratios less than 1, how to make interpretation ?

    Hello all, How do I make interpretation of odds ratio equal to 0.02, given from a logistic model with a binary outcome and let's say 2 treatments...

    Started by NN_STAT‎, 04-27-2013 07:51 AM
    • Replies: 5
    • Views: 36,855
    04-28-2013, 12:33 AM Go to last post
  8. Random Effects Regression vs. Fixed Effects Regression

    I'm having trouble distinguishing when to use random effects versus fixed effects regression. Any thoughts?

    Started by Veronica‎, 12-09-2008 07:44 PM
    • Replies: 6
    • Views: 35,296
    12-10-2008, 08:19 AM Go to last post
  9. Is Fríedman one-way or two-way ANOVA test by ranks?

    Hi, Friedman test is frequently called a one-way or two-way analysis of repeared measure ANOVA on ranks. But what is it, similar to one-way or...

    Started by Dolphin72‎, 10-13-2012 11:40 PM
    • Replies: 2
    • Views: 33,680
    10-15-2012, 12:46 AM Go to last post
  10. Interpretation of Relative risk and confidence interval?

    There were fewer primary events in patients assigned to warfarin than in those assigned to aspirin (24, 1·8% per year vs 48, 3·8% per year, RR 0·48,...

    Started by nana0709‎, 08-28-2010 06:16 PM
    • Replies: 8
    • Views: 33,673
    04-01-2011, 02:10 AM Go to last post
  11. Is my study a case-control or a retrospective cohort study?

    Hi All. I'm dipping my toes into medical research and doing an audit of surgical outcomes. I can't work out whether to describe my study as a...

    Started by bm_mode‎, 12-08-2009 10:46 PM
    • Replies: 2
    • Views: 32,156
    09-30-2010, 07:51 PM Go to last post
  12. omnibus test

    Hi Is it possible to explain me what's an Omnibus Test ??? I find some definitions on Internet but there is'nt some good concrete example ... ...

    Started by viwel‎, 10-28-2008 09:19 AM
    • Replies: 4
    • Views: 29,813
    10-30-2008, 09:00 AM Go to last post
  13. 2-way ANOVA on non-normal, hetergeneous data

    I'm trying to analyze growth data from chicks, and I need to perform the equivalent of a 2-way ANOVA (2x2 design, unequal sample sizes), but my data...

    Started by mogetons‎, 05-23-2011 06:59 PM
    • Replies: 8
    • Views: 29,174
    06-01-2015, 05:19 AM Go to last post
  14. STATA or SAS? Which one should I learn?

    Hello I am currently trying to go a little beyond SPSS by learning either SAS or STATA. My field is psychology and biostatistics. Which one of these...

    Started by sampier85‎, 01-07-2013 04:07 PM
    2 Pages
    1 2
    • Replies: 17
    • Views: 28,161
    03-11-2014, 11:50 AM Go to last post
  15. cox regression v. kaplan-meier

    hi everyone! thanks in advance for your help! i'm studying whether the presence of high v. low hormone levels (of several different hormones)...

    Started by cayetano‎, 04-10-2012 09:05 AM
    kaplan-meier, spss, survival
    • Replies: 4
    • Views: 27,519
    04-26-2012, 10:41 AM Go to last post
  16. Two sample Kolmogorov–Smirnov test

    I would like compare our ideal sample distribution to that from other samples in a study examining the age at onset (AAO) in schizophrenia, which is...

    Started by helpwithstats‎, 10-09-2012 10:00 AM
    • Replies: 2
    • Views: 27,514
    10-19-2012, 10:51 AM Go to last post
  17. Multicollinearity in binary logistic regression

    I have two correlated independent variable and I need to use them both (one as a 'interesting' variable, other one as a control variable). Because of...

    Started by zxc‎, 01-07-2009 04:42 PM
    • Replies: 10
    • Views: 27,465
    01-19-2009, 10:03 PM Go to last post
  18. Quasi-Randomized vs. RCT

    If a study puts participants in the intervention group based on first come first serve (i.e. the first 65 participants who signed up got the...

    Started by Giulia‎, 09-19-2010 06:03 PM
    • Replies: 5
    • Views: 26,850
    09-21-2010, 11:54 AM Go to last post
  19. Constant value in logistic regression

    Hi, My question concerns the constant represents in logistic regression analysis (which can be included/excluded in SPSS). I am trying to...

    Started by arb‎, 10-19-2010 09:55 PM
    • Replies: 3
    • Views: 22,849
    10-20-2010, 01:03 PM Go to last post
  20. Can a cohort study have no control groups (is a clinical series study a cohort)?

    Hi AFAK a cohort study needs a matched control group. However, its definition doesn't necessitate a control group. Moreover, I have read some...

    Started by victorxstc‎, 05-25-2011 04:09 AM
    case series, clinical series, cohort
    • Replies: 5
    • Views: 22,778
    06-22-2011, 11:45 PM Go to last post
  21. Determining significant (or otherwise) difference between 2 rates of change

    Dear Users, I am trying to determine the statistical significant difference (or otherwise) between 2 series of data and am unsure how to proceed....

    Started by Axial‎, 01-01-2012 02:56 PM
    rate, rate of change, significant difference
    • Replies: 7
    • Views: 22,519
    01-09-2012, 02:21 AM Go to last post
  22. How to calculate the Standard deviation of the ratio of two means

    Hi I need to calculate the standard deviation of the ratio between two average values (I have the standard deviation of each average). Steps: -...

    Started by mromano‎, 02-13-2012 10:51 AM
    • Replies: 2
    • Views: 21,090
    02-15-2012, 05:08 PM Go to last post
  23. logistic regression intercept is negative and not significant

    Hi, I have a logistic regression question. My dependent variable is coded 0, 1. When I run my models, the intercept (constant) is negative, and...

    Started by Tucker04‎, 10-22-2009 01:42 PM
    • Replies: 3
    • Views: 21,030
    10-23-2009, 11:52 AM Go to last post
  24. comparing multiple sequences of data over time

    Hi, would really appreciate help on how to test my data! I've three groups (with 5-8 individuals in each group; actually 5 in one and 8 in each of...

    Started by radia‎, 06-01-2011 02:45 PM
    • Replies: 4
    • Views: 20,156
    06-07-2011, 11:47 AM Go to last post
  25. wilcoxon rank sum test or t-test?

    Hello, I have a question for my analysis and reporting. For my analysis, simply said I measured the time needed to achieve sufficient pain...

    Started by noob‎, 08-03-2011 02:12 PM
    • Replies: 8
    • Views: 20,021
    08-07-2011, 07:04 AM Go to last post
  26. Test selection for a ‘marks out of 10’ quiz: Binomial, Fisher, meta-analysis, or ?

    Hello, I have been testing a type of depth of anaesthesia monitor. It involves listening to the EEG (i.e. it’s an electroencephalophone). It’s...

    Started by johnglen‎, 08-19-2012 12:55 PM
    • Replies: 0
    • Views: 19,537
    08-19-2012, 12:55 PM Go to last post
  27. Power analysis for non parametric tests (sample calculation)

    Hi, I am preparing a little presentation on power calculation for parametric tests and it occured to me that I don't know how it works for...

    Started by mousme‎, 10-24-2012 04:58 AM
    • Replies: 2
    • Views: 18,969
    10-24-2012, 10:07 AM Go to last post
  28. Bayes Theorem / Contingency Tables

    In this example, I will walk you through the classic Bayes Theorem question concerning diagnostic tests. Rather than memorize a bunch of formulas...

    Started by JohnM‎, 11-09-2005 11:40 AM
    • Replies: 8
    • Views: 18,287
    01-09-2012, 09:01 AM Go to last post
  29. Any statisticians out here please? £50 voucher offer

    I am doing a survey as part of my MSc project and need someone to review the protocol from a stats point of view, including helping to determine the...

    Started by brownbabygirl‎, 08-11-2014 03:13 PM
    2 Pages
    1 2
    • Replies: 23
    • Views: 16,648
    12-15-2014, 06:28 PM Go to last post
  30. Gene expression analysis - FDR and p-values

    Hi, I'm using Affymetrix microarrays to check if there exist some differences in the gene expression of two group of animals that have been...

    Started by jma‎, 08-07-2012 09:30 AM
    • Replies: 4
    • Views: 16,493
    08-17-2012, 04:34 AM Go to last post
  31. confidence interval interpretation (diagnostic tests)

    If the 95% confidence interval for a relative risk (RR) or an odds ratio (OR) crosses 1, then this is taken as no evidence of an effect = NO...

    Started by adalpra‎, 08-10-2010 04:53 PM
    • Replies: 2
    • Views: 16,329
    08-10-2010, 08:40 PM Go to last post
  32. Should I use Tukey-Kramer or Fisher's LSD post hoc test to follow up my 1-Way ANOVA?

    Dear forum members, As part of a wildlife monitoring study, I ran 1-Way ANOVAs, where the Fixed Factor has three treatments: n1=5, n2=6, n3=5. I...

    Started by Neophyte‎, 12-13-2012 11:26 AM
    • Replies: 3
    • Views: 16,098
    12-15-2012, 01:23 PM Go to last post
  33. median survival time

    Hello, I'm trying to plot a survival curve and I also need median survival time and 95%CI. I specifically need the 95% CI which is not easy to...

    Started by noob‎, 06-06-2010 05:08 PM
    • Replies: 8
    • Views: 15,892
    06-13-2010, 01:28 AM Go to last post
  34. Should I use an ANCOVA or two t-tests?

    Hi I'm studying the level of an ion in patients compared with matched controls. My results are categorized by gender and cohort/control...

    Started by victorxstc‎, 07-30-2011 06:36 PM
    • Replies: 10
    • Views: 14,871
    10-04-2011, 01:41 PM Go to last post
  35. What statistical test should I use?

    hello guys, I am doing some statistics and I am a little confused on which test is the most appropriate to calculate the P value. I have a...

    Started by scerab‎, 01-28-2011 12:13 PM
    2 Pages
    1 2
    • Replies: 25
    • Views: 14,513
    03-01-2011, 04:43 PM Go to last post
  36. Difference between Sensitivity and Statistical Power?

    Hi, Could anyone point me towards an explanation of the difference between Sensitivity (as described here:...

    Started by simshef‎, 05-14-2009 06:34 AM
    • Replies: 3
    • Views: 14,248
    05-18-2009, 11:28 AM Go to last post
  37. weighted standard error of the mean

    Hi, I am trying to calculate some statistical properties pertaining to mobility of cargo inside cells for my research, but due to my poor...

    Started by jvaughan5‎, 02-26-2008 01:49 PM
    • Replies: 1
    • Views: 14,247
    09-13-2009, 07:19 AM Go to last post
  38. What do YOU mean by "statistically significant"?

    Here's a question more about communication than statistical methods. I've experienced that the term "statistically significant" is used often by...

    Started by jawon‎, 10-06-2008 06:19 PM
    2 Pages
    1 2
    • Replies: 25
    • Views: 13,524
    10-22-2008, 04:40 PM Go to last post
  39. How to make a heatmap in R for a microarray data?

    Hi guys, I have been given a microarray data for which I need to figure out a heatmap. Unfortunately I have never had a chance and experience in...

    Started by LigongKarlChen‎, 03-08-2010 11:35 AM
    • Replies: 2
    • Views: 13,421
    03-08-2010, 03:16 PM Go to last post
  40. A Question regarding the Kaplan Meier survival curve.

    Hello guys I have a set of epidemiological data for a group of patients whom were followed up for a specific time period. The mortality rate was...

    Started by scerab‎, 01-20-2011 02:14 AM
    • Replies: 5
    • Views: 13,356
    02-25-2013, 02:11 AM Go to last post
  41. equal or unequal sample size ?

    I have a simple theoretical question... Let's say I have a sample of 30 subjects from group A and 150 from group B, and I want to run a t-test. ...

    Started by NN_STAT‎, 02-14-2012 07:56 AM
    • Replies: 6
    • Views: 12,914
    02-15-2012, 09:06 AM Go to last post
  42. best biostatistics textbook?

    I have Health and Numbers. I'd like to get another book to supplement. Recommendations? Looking for clear and simple! Thanks!

    Started by kalbright36‎, 09-29-2005 09:58 PM
    • Replies: 3
    • Views: 12,697
    10-05-2005, 11:26 PM Go to last post
  43. Mann-Whitney U and Bonferroni Correction

    I recently presented some work in my department in which my colleagues and I had applied a Mann-Whitney U test for multiple pairwise comparisons. We...

    Started by Zachariah‎, 04-05-2013 01:27 PM
    bonferroni correction, mann-whitney u, non-parametric
    • Replies: 3
    • Views: 12,626
    04-08-2013, 09:31 AM Go to last post
  44. Is my study case-control or retrospective cohort?

    Hi AFAIK if we split the sample by the exposure, it is retrospective cohort; and if we split it by the disease, it is case control. I am...

    Started by victorxstc‎, 05-09-2011 11:20 AM
    case control, cohort, exposure, study design
    • Replies: 8
    • Views: 12,479
    05-13-2011, 11:18 AM Go to last post
  45. Clinical Significant vs Statistical Significant

    Hi Guys, I read some strong criticism about "statistical significance". Some researchers claim that statistical significance is useless. in...

    Started by WeeG‎, 04-09-2011 07:33 AM
    • Replies: 8
    • Views: 12,255
    07-25-2011, 12:43 PM Go to last post
  46. How to adjust data of confounding variables adjusting diabetes to BMI and age

    I am doing a study of pregnant diabetes women. There are 3 types Type 1 , 2 and gestational. Then various ages and bmis. Outcomes study include type...

    Started by FSNWRM‎, 02-21-2012 01:34 AM
    • Replies: 6
    • Views: 11,783
    02-22-2012, 08:41 AM Go to last post
  47. Test for linear trend in odds ratio in linear regression

    I often see epidemiological studies where a continuous variable has been divided into quantiles and the odds ratios for each quantile compared with a...

    Started by Disvengeance‎, 07-13-2014 09:50 AM
    • Replies: 10
    • Views: 11,727
    09-04-2015, 01:16 PM Go to last post
  48. Survival Analysis with Interval Censored Data

    Dear All I'm trying to do a survival analysis with interval censored data. The data are basically eye pressure measurements at certain...

    Started by SiBorg‎, 03-05-2012 12:37 PM
    • Replies: 13
    • Views: 11,612
    04-15-2014, 03:06 AM Go to last post
  49. Logistic regression with continuous variables

    I have levels of eight biochemical markers (continuous variables) and want to determine whether each marker helps to predict the presence or absence...

    Started by rbody‎, 10-06-2008 03:54 PM
    • Replies: 4
    • Views: 11,574
    10-07-2008, 05:26 AM Go to last post
  50. Concordance index in survival analysis (cox regression) adjusted for competing risk

    Hello everybody! First of all this is truely a wonderful place for discussion about statistics. I have been looking here from time to time and I...

    Started by Sirikon‎, 01-11-2012 09:33 AM
    competing risks, concordance index
    • Replies: 3
    • Views: 11,368
    01-17-2012, 12:37 PM Go to last post
  51. Arrow Interpreting Cox proportional hazards regression p values

    Hi guys, I have been testing the hypothesis for difference of survival between four different classes by using coxph function of survival package...

    Started by jacks‎, 02-16-2011 02:39 AM
    • Replies: 2
    • Views: 10,844
    02-16-2011, 05:35 AM Go to last post
  52. Can you calculate the odds ratio for a 2X3 Chi Square?

    I know technically you can do the calculation, but what I really want to know is does this give you any statistically relevent information that you...

    Started by billkarr‎, 05-15-2010 08:19 AM
    • Replies: 1
    • Views: 10,704
    05-15-2010, 06:03 PM Go to last post
  53. Multiple Ailments

    1 in 24 people in the US are diagnosed with COPD, 1/314 with Parkinsons, 1 in 12 with heart disease. What is the chances for a person to have a 3...

    Started by Blueray123‎, 08-24-2013 12:01 PM
    • Replies: 5
    • Views: 10,602
    08-31-2013, 04:33 PM Go to last post
  54. data analysis for retrospective cohort study

    Hi!! Im embarrassed to be asking v basic questions :o I proposed a study topic for my group assignment, looking at cancer rates between...

    Started by niledee‎, 04-08-2011 07:17 AM
    • Replies: 2
    • Views: 10,545
    04-09-2011, 06:13 AM Go to last post
  55. diagnostic testing and sample size calculation

    Hello everyone, I did a study evaluating 2 screening tools (questionnaires) compared to a reference in the same sample of patients. So all the...

    Started by noob‎, 05-19-2012 03:17 PM
    • Replies: 4
    • Views: 10,412
    05-31-2012, 06:22 PM Go to last post
  56. Data Format for Repeated Measures AnoVa/SPAnoVa

    Hi everyone, I am a newcomer to the forum, SPSS and stats in general. Having followed the inbuilt tutorials in SPSS (V15) and using Julie Pallant's...

    Started by Random_Man‎, 02-17-2009 01:30 PM
    • Replies: 5
    • Views: 10,411
    02-20-2009, 05:35 AM Go to last post
  57. General two-way ANOVA questions

    Hi, I have the following factors in my data: pretreatment (yes or no), drug_dose (1, 2, 3, 4) and neurochemical levels (dependent variable). ...

    Started by sfishe‎, 12-20-2010 06:10 PM
    • Replies: 4
    • Views: 10,379
    12-21-2010, 03:16 AM Go to last post
  58. How to do post hoc tests in logistic regression?

    I looked at whether participants recycled after being subjected to a given message. There were three groups: a Control group, group A, and group B. ...

    Started by ionpattern‎, 03-29-2012 08:13 PM
    logistic regression, post hoc test
    • Replies: 2
    • Views: 10,264
    04-01-2012, 07:40 PM Go to last post
  59. Question Repeated measure analysis using SAS (crossover design)

    I joined the forum in desperation as I urgently need help and I hope there is somebody out there that will be able to help me.:shakehead Some...

    Started by Biostatistician‎, 05-12-2009 01:56 AM
    • Replies: 1
    • Views: 10,263
    09-25-2011, 08:46 PM Go to last post
  60. Likelihood ratio in Cox regression analysis?

    I have done a great deal of research without any success regarding the interpretation of likelihood ratio (LR) test in Cox regression analysis. If...

    Started by arkiaamu‎, 11-19-2012 09:42 AM
    • Replies: 1
    • Views: 10,119
    11-19-2012, 06:01 PM Go to last post

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