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Forum: Biostatistics

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

  1. Relative Risk in logistic regression

    Hi all, I am very grateful to all those who write to me 1) how i can obtain relative risk (risk ratio) in logistic regression in R. 2) how to...

    Started by aminreza‎, 01-30-2013 06:36 AM
    • Replies: 3
    • Views: 2,670
    03-07-2013, 01:17 AM Go to last post
  2. Dunnett's Table of Critical Values

    Hi all, I'm new to the forum, and verrry new to stats. I just love these places, lol. Well, here it goes. Does anybody have a link to the NIST...

    Started by BrainExploding‎, 03-06-2013 12:18 PM
    critical values, dunnett t test, dunnett table, table of critical values
    • Replies: 2
    • Views: 4,800
    03-06-2013, 01:11 PM Go to last post
  3. Weibull in literature

    Hey guys, Could someone recommend (text-)books or classical/overview articles where it is stated that the Weibull distribution is an appropriate...

    Started by Jacov‎, 03-05-2013 06:52 PM
    • Replies: 0
    • Views: 1,457
    03-05-2013, 06:52 PM Go to last post
  4. Averaging fitted slopes

    I'm sure this statistical issue has been solved before, but I had a heck of a time googling it. I hope someone here can recommend a method for...

    Started by meatsafemurderer‎, 03-05-2013 08:44 AM
    • Replies: 0
    • Views: 1,399
    03-05-2013, 08:44 AM Go to last post
  5. Doing Bonferroni Correction using stats software

    Hi, I am comparing the effect of two compounds on the behavior of an insect and generate data with time vs different dosages of the compounds. I...

    Started by artery‎, 03-05-2013 01:26 AM
    • Replies: 0
    • Views: 1,409
    03-05-2013, 01:26 AM Go to last post
  6. Incidence rates - best way to do trend analysis?

    Hi everyone, I have a series of admitted patient data and notifiable diseases data over a time period for 3 different study areas. For each year,...

    Started by wernie‎, 03-05-2013 12:25 AM
    incidence, incidence rate, trend analysis
    • Replies: 0
    • Views: 2,989
    03-05-2013, 12:25 AM Go to last post
  7. Ways to find interaction effects of 2 nominal variables on nominal dependant variable

    Hello I am trying to doing analysis of interaction effects of 1-7 dichotomous or polychotomous dependent variables (nutrition type, either 2 or 3...

    Started by bearclaw‎, 03-02-2013 02:34 PM
    catagorical data, contingency tables, interaction, logistic regression, nominal data analysis
    • Replies: 2
    • Views: 3,370
    03-04-2013, 09:43 PM Go to last post
  8. Help with understanding evolutionary conservation

    Greetings, I am working with a dataset with measurements of the %amino acid conservation (DV) for 62 ordered glycosylation sites (IV - 62 levels)...

    Started by CrystalH‎, 03-01-2013 05:18 PM
    • Replies: 0
    • Views: 1,172
    03-01-2013, 05:18 PM Go to last post
  9. Multiple comparisons correction help

    Hi, I have already asked a similar question but did not explain my problem in entirety. Any help would be greatly appreciated! I am analyzing...

    Started by JonoBone‎, 02-28-2013 07:44 PM
    boneferroni correction, multiple comparisons
    • Replies: 3
    • Views: 1,862
    03-01-2013, 10:43 AM Go to last post
  10. Question Standardization of data for cannonical correspondence analysis

    do we need to transform environmental parameter data and species data to do CCA and how should the transformation be done? one more should we take...

    Started by balu‎, 03-01-2013 05:18 AM
    • Replies: 0
    • Views: 1,606
    03-01-2013, 05:18 AM Go to last post
  11. Post [HELP REQUESTED] Calculating Sample Size Based on a Pilot Study [HELP REQUESTED]

    Good morning Talk Stats, I come to you after many hours spent on the web researching and working hard to find a solution. So far, I have been...

    Started by Strategist‎, 02-28-2013 12:10 PM
    calculation, immunology, sample size
    • Replies: 2
    • Views: 1,690
    02-28-2013, 04:09 PM Go to last post
  12. Average of 4 standard errors in replicated plot experiment

    Hello everybody! After looking for a solution for good 2 hours, I decide just to ask for help in a nice forum. I have a field experiment with 4...

    Started by SoilScientist‎, 02-27-2013 02:04 PM
    • Replies: 0
    • Views: 1,237
    02-27-2013, 02:04 PM Go to last post
  13. Significant Outliers

    I have measured 4 characteristics for ~600 individuals (2 biological replicates per individuals). Some of the characteristics are not normally...

    Started by JJS‎, 02-26-2013 12:06 PM
    • Replies: 1
    • Views: 1,021
    02-26-2013, 02:25 PM Go to last post
  14. Cell growth - One way or two way anova?

    Hi all! I'm having questions regarding some results I've got. I have been counting cells twice a day for a week. There are three different cell...

    Started by jajamensan‎, 02-25-2013 08:04 AM
    anova growth
    • Replies: 2
    • Views: 3,540
    02-25-2013, 02:03 PM Go to last post
  15. 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: 13,373
    02-25-2013, 02:11 AM Go to last post
  16. Retrospective data and fixed effects models

    I have some questions about the best analysis design for retrospective data. The data are the relationship and marriage biography of a person and a...

    Started by bjoern‎, 02-24-2013 03:19 AM
    • Replies: 0
    • Views: 1,422
    02-24-2013, 03:19 AM Go to last post
  17. Patient survey - what is the right statistical test?

    I am asking patients, with a particular condition called Critical Limb ischaemia, what their preferences are (ranked preferences). Patients are asked...

    Started by benedictphillips‎, 02-23-2013 05:51 AM
    • Replies: 1
    • Views: 1,271
    02-23-2013, 11:07 AM Go to last post
  18. retrospective power/sample size analysis for a skewed distribution & mann whitney

    Hi, Here is my problem: I have performed a study comparing the effect of administration of 2 different doses of morphine on the quality of the...

    Started by Mando‎, 02-23-2013 09:31 AM
    • Replies: 0
    • Views: 3,283
    02-23-2013, 09:31 AM Go to last post
  19. Chi square or logistic reg test? Groups are different only in 2 demographic data.

    I have to compare rates of any breastfeeding (categorical variables: yes and No) between two groups of women. I recruited the sandard care group...

    Started by shahla‎, 02-22-2013 06:29 PM
    • Replies: 2
    • Views: 1,869
    02-22-2013, 07:40 PM Go to last post
  20. Looking to see if there is a correlation between qualitative and quantitative data

    Hi, I have an environmental science issue where I'm trying to see if there is a correlation between some qualitative and quantitative data....

    Started by nimbus‎, 02-21-2013 07:42 PM
    • Replies: 0
    • Views: 2,385
    02-21-2013, 07:42 PM Go to last post
  21. ROC curve and comparison of data from serial tests.

    Hello! With the premise that I am a simple biotechnologist and I've never studied biostatistics at all, I have been assigned the task of analyzing...

    Started by zuzi‎, 02-20-2013 07:05 AM
    interpretation, roc, serial tests
    • Replies: 5
    • Views: 2,378
    02-21-2013, 09:39 AM Go to last post
  22. comparing multiple observations with single

    Hi all, I want to compare multiple rows(observations) with single column (variable) in sas. How can i do it? is proc compare helpful for that? need...

    Started by Genetist‎, 02-20-2013 01:37 AM
    • Replies: 0
    • Views: 1,332
    02-20-2013, 01:37 AM Go to last post
  23. AIC for multivariate linear regression

    I am hoping to use AIC to evaluate multivariate linear regression models including interaction terms. Is this possible? If so, how does one determine...

    Started by kpete‎, 02-16-2013 01:22 PM
    • Replies: 2
    • Views: 4,431
    02-18-2013, 08:31 PM Go to last post
  24. How to use a meta-analysis to assess the equivalence of two different procedures?

    I'm making a comparison of two surgical procedures, and I want to know how I can analyze the data I have for a meta-analysis. The overall surgical...

    Started by gustav‎, 02-18-2013 05:31 PM
    equivalence testing, meta analysis, meta-analysis, non-inferior
    • Replies: 0
    • Views: 1,147
    02-18-2013, 05:31 PM Go to last post
  25. Analysis of continuous independent variable and binary dependent variable

    I am conducting a study into the healing of burn wounds. To give a brief background: Following a burn, the necrotic (dead) tissue is surgically...

    Started by keno.mentor‎, 01-02-2013 07:41 AM
    • Replies: 4
    • Views: 7,234
    02-18-2013, 10:39 AM Go to last post
  26. Adjusted Chi-squared test for clustered binary / categorical data

    I'm looking for some assistance in statistical analysis with R (ideally), but also some general stats advice. This follows from a review which...

    Started by ugm6hr‎, 02-17-2013 10:08 AM
    chi-squared, clustering, proportions
    • Replies: 0
    • Views: 3,464
    02-17-2013, 10:08 AM Go to last post
  27. Hierarchical clustering and data standarization

    Hi! I'm going to use a hierarchical clustering (Ward minimum variance method) to find relationships in plants phenotype changes for egzample...

    Started by gocha_sol‎, 02-08-2013 06:04 PM
    • Replies: 5
    • Views: 1,938
    02-16-2013, 04:34 AM Go to last post
  28. SPSS log-rank comparing 4 survival curves

    I was completing a Kaplan-Meier analysis using SPSS. The variable has 4 different outcomes. SPSS will still allow me to use the log-rank test to...

    Started by lazers‎, 02-12-2013 12:47 PM
    • Replies: 1
    • Views: 3,967
    02-14-2013, 09:42 PM Go to last post
  29. Test if two proportions are equal

    Hi all, This is probably a pretty simple question, but I'm getting myself confused... I have two "yes/no variables", and I need to determine if...

    Started by katiejackson‎, 02-08-2013 10:12 AM
    • Replies: 8
    • Views: 1,887
    02-08-2013, 01:36 PM Go to last post
  30. Statistical design for minimum inhibitory concentration (MIC)

    Post deleted. Sorry for the inconvenience.

    Started by Ben Tambling‎, 02-08-2013 09:44 AM
    mic, statistical design
    • Replies: 0
    • Views: 1,703
    02-08-2013, 09:44 AM Go to last post
  31. How to test if the odds of success are significantly different from zero

    Hi all, Suppose I have a model below (in R): glmer(Y~X + (1|subject), family="binomial", data=dat) Where Y is the binary outcome variable...

    Started by pydbl‎, 02-08-2013 12:19 AM
    binary dependent variable, logistic regression, odds
    • Replies: 2
    • Views: 1,838
    02-08-2013, 08:53 AM Go to last post
  32. Red face calculate sample size for sensitivity and specificity in a new diagnositic test

    My question is difficult to me, I had read an article about how to calculate sample size the foot note tole me"" ε = required absolute precision...

    Started by mmchocolateyy‎, 02-06-2013 02:44 PM
    precision, sample size, sensitivity, specificity
    • Replies: 0
    • Views: 4,050
    02-06-2013, 02:44 PM Go to last post
  33. Which test to use?

    Hi, I have a question in hand that people from a population is sampled to see if they have certain characteristics, say wearing red pant, yellow pant...

    Started by cindy‎, 01-03-2013 08:24 AM
    • Replies: 2
    • Views: 1,557
    02-05-2013, 04:52 AM Go to last post
  34. detection rate question

    Hi, I have sort of a backwards question. I have a calculated detection rate and its standard error, and I know the number of positives that were...

    Started by john123‎, 02-04-2013 06:46 PM
    confidence intervals, detection rate, standard error
    • Replies: 1
    • Views: 1,081
    02-04-2013, 08:08 PM Go to last post
  35. Transformation to improve normality

    Hi, I have a problem with some data that I am trying to analyse in a Repeated Measures design. I have 5 conditions (variables), 13 subjects, data...

    Started by rav8‎, 01-31-2013 11:47 PM
    kolmogorov-smirnov, normality, repeated measures, shapiro-wilk, tranformation
    • Replies: 7
    • Views: 4,109
    02-04-2013, 07:10 PM Go to last post
  36. Compare a proportion to a fixed number

    Hi, I am struggling with a little problem. I have a group of people that eat food from a personal ration box over some days. They will not eat the...

    Started by Pardosa‎, 02-04-2013 04:37 AM
    • Replies: 1
    • Views: 1,436
    02-04-2013, 05:36 AM Go to last post
  37. Comparing FISH scores

    hi there, Is there a statistical test I can do to prove that two FISH scores are reliable? Only one slide is used, with two independent...

    Started by a5027264‎, 02-03-2013 11:52 AM
    • Replies: 0
    • Views: 975
    02-03-2013, 11:52 AM Go to last post
  38. Calculating minimum proportion relevant for micro-simulation modeling

    Hello, I am new to this site, so please forgive me if this is posted in the wrong section. I have a question that is related to the area of...

    Started by phill‎, 02-01-2013 01:50 PM
    • Replies: 1
    • Views: 2,698
    02-01-2013, 05:03 PM Go to last post
  39. genetic purity test

    Hi to everyone, we did genetic purity test with SNP (44) markers for 200 samples with 8 individuals in each sample to know how pure those 8...

    Started by Genetist‎, 01-31-2013 10:48 AM
    • Replies: 0
    • Views: 1,574
    01-31-2013, 10:48 AM Go to last post
  40. Sample size for mixed models

    Hello I have a sample size question. Let's say that I want to design a trial to compare two treatments. Usually, I would use the t-test, and thus...

    Started by NN_STAT‎, 01-15-2013 05:31 AM
    • Replies: 2
    • Views: 7,062
    01-30-2013, 08:52 AM Go to last post
  41. Hazard ratio and confidence intervals - quick question!

    Hi, I have a quick question:) If a confidence interval crosses 1.0 does that mean that automatically mean the p value is not significant? In...

    Started by nmr00‎, 01-29-2013 07:49 PM
    • Replies: 0
    • Views: 6,708
    01-29-2013, 07:49 PM Go to last post
  42. Help with sample size calculations

    Hello I need some help with sample size calculations... I have a planned experiment, with a new surgical device. In a pilot study, the...

    Started by NN_STAT‎, 01-22-2013 06:41 PM
    • Replies: 3
    • Views: 1,577
    01-29-2013, 03:08 PM Go to last post
  43. Not sure which ANOVA to use (mixed model likely)

    Hello all, I am new to the board and more versed with multidimensional stats rather than ANOVAs. I will present a simplified version of my...

    Started by hydrocynus‎, 01-28-2013 01:11 AM
    • Replies: 0
    • Views: 1,161
    01-28-2013, 01:11 AM Go to last post
  44. Analysis of individual and pooled samples

    I have a small data set that includes individual and pooled samples. It looks like this: School A (one individual tested) Positive for infection:...

    Started by Alpha7383‎, 01-25-2013 02:13 PM
    • Replies: 4
    • Views: 1,959
    01-27-2013, 11:28 PM Go to last post
  45. Handling data from 2 experiments

    Dear all, I have 2 sets of data from 2 behavioral experiments in rats. The study design, procedures and technicians were the same between both...

    Started by urukai‎, 01-25-2013 07:39 AM
    • Replies: 3
    • Views: 1,790
    01-26-2013, 05:21 PM Go to last post
  46. Physics-style Repeated Measures of multiple predictor variables in survival analysis?

    I have inherited a longitudinal dataset where 5 different continuous independent variables were measured multiple times daily for 28 days in...

    Started by Sturu‎, 01-26-2013 12:51 PM
    repeated measures, survival, time series
    • Replies: 0
    • Views: 1,335
    01-26-2013, 12:51 PM Go to last post
  47. Post Multi-rater agreement statistic

    Hi all, This is my first post question. I have a question on multirater agreement. Raters are given a description of the condition of the each...

    Started by marioidsouza‎, 01-22-2013 08:24 PM
    agreement, kappa, multiraters, raters
    • Replies: 4
    • Views: 1,975
    01-23-2013, 05:42 PM Go to last post
  48. How to become a statistician (Epidemiologist) If I have not measured in Statistics

    :yup: Hello There I am a masters student in health science. By health science I mean a mix of epidemiology, psychology, and health policy. It is a...

    Started by sampier85‎, 01-14-2013 11:30 PM
    epidemiology, statistics
    • Replies: 4
    • Views: 5,089
    01-17-2013, 12:34 PM Go to last post
  49. Time scales in longitudinal studies using GEE (binary outcome)

    I have a question regarding the use of timescales when evaluating change over time, specifically using logistic regression with generalized...

    Started by Theresia‎, 01-16-2013 12:16 PM
    • Replies: 1
    • Views: 1,498
    01-17-2013, 03:35 AM Go to last post
  50. Testing effectiveness of diagnostic test?

    Hi! I need some help solving a statistics question. An RCT has been conducted to assess the effectiveness of a diagnostic test to decide if...

    Started by zutev‎, 01-15-2013 01:05 PM
    • Replies: 3
    • Views: 1,529
    01-15-2013, 04:01 PM Go to last post
  51. Protein expression analysis/ FDR vs p-value?

    Iím testing 754 protein's expression difference between two groups. Iím using either empirical Bayes (also tried non-parametric MWU-test) with...

    Started by Krisu‎, 01-10-2013 09:17 AM
    • Replies: 7
    • Views: 3,916
    01-11-2013, 02:21 PM Go to last post
  52. Cohen's kappa or Fleiss kappa or both?

    Hi all, I am trying to compare 2 instruments, A and B, against the gold standard. The measurement outcome is dichotomous. 2 different raters,...

    Started by lendel‎, 01-10-2013 10:30 AM
    agreement, interrater reliability, kappa
    • Replies: 1
    • Views: 5,535
    01-10-2013, 12:05 PM Go to last post
  53. Interaction and confounding in logistic regression

    Hope someone here can help me out with the following problem! I’m looking for explanatory factors for a certain dichotomous health outcome, the...

    Started by anker‎, 01-10-2013 05:53 AM
    confounding, interaction, logistic regression
    • Replies: 0
    • Views: 1,487
    01-10-2013, 05:53 AM Go to last post
  54. Meta-analysis using unpublished randomised trials

    Hi, I am intersted to do a meta-analysis, have data set from about 50 experiments, mostly unpublished, some published in the form of reports, but non...

    Started by sania‎, 01-06-2013 08:08 PM
    • Replies: 3
    • Views: 1,354
    01-06-2013, 09:21 PM Go to last post
  55. Measuring Variability - Research Experiemtn

    Hi guys I'm looking at the variability of temperatures that can stimulate pain in different subjects and whether this variability decreases at...

    Started by nianu‎, 01-06-2013 10:47 AM
    • Replies: 0
    • Views: 1,018
    01-06-2013, 10:47 AM Go to last post
  56. Birds - racial segregation - want to check my method please.

    I have data from four nearby sites, on Redshanks, (birds) that were captured and ringed during the winter over a 30-odd year period using two...

    Started by MW0CBC‎, 01-04-2013 12:49 PM
    • Replies: 11
    • Views: 2,166
    01-06-2013, 10:46 AM Go to last post
  57. Post Relative Risk Ratio (RRR) Analysis with a Continuous Predictor

    Hi, I am hoping that someone can help me with a relative risk ratio analysis. I'm trying to assess the ability of a continuous variable to predict a...

    Started by evopass‎, 12-06-2012 04:33 AM
    categorical data analysis, odds ratio, regression analysis, relative risk, risk ratio
    • Replies: 7
    • Views: 9,880
    01-04-2013, 09:25 AM Go to last post
  58. Replicates for a Dose-Response Test

    Hi, I need to calculate the number of replicates for a Dose-Response Test in Interference Testing. But I donít understand the equation: There...

    Started by Pipa‎, 12-30-2012 08:16 AM
    • Replies: 2
    • Views: 2,045
    01-03-2013, 01:22 PM Go to last post
  59. Comparing percentages of 2 paired groups

    Hi, I have tried to find the answer to my question in the forums and think I have the answer - just want to double check, if that's ok... I am...

    Started by rhurf‎, 01-02-2013 08:05 AM
    • Replies: 1
    • Views: 1,992
    01-02-2013, 09:05 AM Go to last post
  60. Making metabolite samples with different volumes comparable prior to paired T-test

    Hi, I have metabolite measurements from tumor patients comparing samples from the tumor tissue (3 replicates per patient) against nearby...

    Started by garfield42‎, 12-18-2012 12:05 PM
    centering, paired comparisons, standardization, t-test
    • Replies: 1
    • Views: 1,436
    01-01-2013, 11:56 PM Go to last post

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