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Forum: Biostatistics

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

  1. Direct Fertility calculation - Error estimation

    Dear All, how to estimate the sampling error of fertility?...which is calculated from a representative sample survey using the direct method from...

    Started by edhunter‎, 11-15-2011 05:29 AM
    • Replies: 0
    • Views: 1,572
    11-15-2011, 05:29 AM Go to last post
  2. Talking Comparing percentages

    I am doing a study, and have gathered the following data: A patient population was divided into 3 categories: Young patients (n=19) / Middle...

    Started by systat‎, 08-20-2011 03:39 PM
    percentage, percentage comparison
    • Replies: 2
    • Views: 1,892
    11-13-2011, 08:58 PM Go to last post
  3. power calculation

    Hi there! help if you can!! how can i calculate power of the study where i have only categorical data? Example: association study with two...

    Started by muraveinik‎, 11-05-2011 02:22 PM
    • Replies: 2
    • Views: 2,774
    11-10-2011, 10:01 AM Go to last post
  4. Biological data - how would you analyse this non-parametrically?

    I tagged and tracked some fish in a stream and recorded their locations on multiple occasions. For each location I have data (interval and nominal)....

    Started by amber33‎, 11-05-2011 08:20 PM
    • Replies: 4
    • Views: 2,001
    11-09-2011, 11:20 PM Go to last post
  5. How do you get estimates for time-to-event using a Cox PH model?

    I am trying to get an estimate of time-to-event for each observation in the dataset in the same units (days) as the original time units by using a...

    Started by mrc112‎, 11-09-2011 07:56 AM
    • Replies: 0
    • Views: 2,400
    11-09-2011, 07:56 AM Go to last post
  6. Unequal variance and non-gaussian datasets?

    Hi, I am working on my thesis project and have come across a problem with the statistics which I am looking for a bit of guidance. I have 2...

    Started by peak00‎, 11-04-2011 12:29 PM
    • Replies: 0
    • Views: 1,493
    11-04-2011, 12:29 PM Go to last post
  7. Anova ?

    Hi everyone I have a set of entropy values calculated for a gene, across the length of the gene, in 3 codon positions which is formatted as...

    Started by dejmail‎, 11-04-2011 06:05 AM
    • Replies: 2
    • Views: 2,200
    11-04-2011, 08:59 AM Go to last post
  8. Question Handling erroneous multiple responses: safe to round up or round down?

    Hi all, First post here- hope I am in the right place. I am working on a public health data set that is looking at a particular set of risk...

    Started by FridaCTL‎, 11-03-2011 11:39 AM
    • Replies: 0
    • Views: 1,730
    11-03-2011, 11:39 AM Go to last post
  9. Neuroembryology stats

    I would appreciate some help on how to model my data and which tests to use to prove significance. Essentially we took babies with cranial defects...

    Started by jnewman‎, 11-02-2011 08:13 PM
    • Replies: 0
    • Views: 1,816
    11-02-2011, 08:13 PM Go to last post
  10. Which test to use?

    Hi everybody, I was told to statistically confirm my results. Unfortunately I am not very good at statistics, so I hope you guys can help me with...

    Started by knabberknut‎, 11-02-2011 09:58 AM
    • Replies: 0
    • Views: 2,010
    11-02-2011, 09:58 AM Go to last post
  11. mann whitney U vs graphs?

    Hello all, I have some pre and post data that I'm analysis but have a slight problem. during a 3 month period patients answered an anonymous...

    Started by GStein‎, 11-01-2011 10:59 AM
    • Replies: 0
    • Views: 2,066
    11-01-2011, 10:59 AM Go to last post
  12. which test to use

    dmf index(decay missed filled) used in oral hygiene or oral examination we want to compare the dmf index that is a numerical valve with 1.age...

    Started by throbbingheart01‎, 10-27-2011 11:12 AM
    • Replies: 3
    • Views: 2,176
    11-01-2011, 05:44 AM Go to last post
  13. Matching and Randomization for a Three-Armed RCT

    Hello all- I need some assistance conceptualizing how to run matching and randomization for an RCT I'm working on. The overarching question...

    Started by Salone‎, 10-26-2011 12:07 PM
    • Replies: 0
    • Views: 3,496
    10-26-2011, 12:07 PM Go to last post
  14. selecting proper analysis model

    Hello, I'm looking for some help on a research project I'm working on. I've been given a data set on the adoption of electronic health records...

    Started by helpmeunderstand‎, 10-25-2011 05:26 PM
    • Replies: 1
    • Views: 2,273
    10-25-2011, 07:13 PM Go to last post
  15. Selecting appropriate statisitical analysis - research

    First, let me say that I am new to this forum. If I have missed any important steps or protocols, please let me know. A brief description of my...

    Started by aboveliquidice‎, 10-25-2011 04:30 PM
    • Replies: 3
    • Views: 2,031
    10-25-2011, 07:08 PM Go to last post
  16. Two-way ANOVA, should I compare by column, row or neither?

    Hi guys, I'm trying to analyze my data using two-way ANOVA via Prism 5.0. I don't quite understand the examples provided by Prism's help menu because...

    Started by jyanglaststar‎, 10-25-2011 04:06 PM
    • Replies: 0
    • Views: 2,263
    10-25-2011, 04:06 PM Go to last post
  17. Are there 2 ways to calculate logrank probability?

    Dear forum readers, I am calculating survival in two group of patients. For comparison between two survival curves, log rank test is recommended....

    Started by Markica85‎, 10-25-2011 03:46 PM
    • Replies: 0
    • Views: 5,940
    10-25-2011, 03:46 PM Go to last post
  18. Question MANCOVA with all predictors being continuous variables - how to follow-up?

    Dear Stats Experts, I would be most grateful for any thoughts on the following: I have a cross-sectional dataset with 7 outcome variables from...

    Started by antonzzz‎, 10-22-2011 12:38 PM
    discriminant analysis, mancova, manova, multivariate
    • Replies: 3
    • Views: 3,396
    10-24-2011, 04:41 AM Go to last post
  19. Cox PH estimation problem (with real data)

    I have data on a spell duration which I would like to analyze with the Cox PH model. The defining feature of the data is the year (or date to be...

    Started by professor‎, 10-17-2011 04:46 PM
    • Replies: 1
    • Views: 2,215
    10-22-2011, 10:56 AM Go to last post
  20. How to analyze survival data with type 1 censoring?

    I am working with survival data from a population-based sample of the general very old population. The participants were interviewed, their relatives...

    Started by CarlAH‎, 10-21-2011 07:49 AM
    • Replies: 2
    • Views: 2,607
    10-21-2011, 06:21 PM Go to last post
  21. Comparing a value to two candidate values

    Hello, I am looking for the appropriate statistical test to answer the following type of question. If I have a true value for a variable for an...

    Started by zakmancrothers‎, 10-21-2011 02:54 PM
    • Replies: 1
    • Views: 1,876
    10-21-2011, 03:04 PM Go to last post
  22. Statistical analysis for Homeostatic proliferation

    Hi guys, I'm hoping someone can tell what is the right statistical analysis to perform on my data set. I'm currently using Graph Pad prism to...

    Started by AWSL‎, 10-19-2011 04:37 PM
    • Replies: 4
    • Views: 2,097
    10-20-2011, 02:23 AM Go to last post
  23. contingency table: categories are not mutually exclusive, and data is not all paired

    Hi, I'm confused about what test I should be using and hope someone can help. Data: I have data from microbiological samples where the...

    Started by radia‎, 10-17-2011 02:11 PM
    contingency table, mcnemar's, not mutually exclusive, spss, unpaired
    • Replies: 0
    • Views: 6,345
    10-17-2011, 02:11 PM Go to last post
  24. Need help on statistical analysis

    Hello all, i'm really new in research. This is my first research project. I'm in the process of writing my proposal. I will be comparing outcomes...

    Started by fahmiabad‎, 09-09-2011 09:39 AM
    • Replies: 5
    • Views: 2,541
    10-17-2011, 04:32 AM Go to last post
  25. help to find out a statistical method

    hi , my name is harsha, and i am a medical doctor by profession and i need your help. i am currently involved in a research project in my...

    Started by harsha kumar‎, 09-16-2011 09:34 PM
    • Replies: 4
    • Views: 2,051
    10-17-2011, 04:13 AM Go to last post
  26. Help please, urgent, trend question?

    I have collected oral cancer data from hospital cancer registry for three years. The number of oral cancer and all cancer(which include oral cancer)...

    Started by medsonia‎, 10-16-2011 07:50 AM
    • Replies: 2
    • Views: 1,944
    10-17-2011, 03:48 AM Go to last post
  27. Exclamation Help needed! Primary vs Secondary outcomes

    Why is a statistically significant Primary Outcome taken to be conclusive, but a statistically significant Secondary Outcome is considered merely a...

    Started by lattimer‎, 10-16-2011 06:10 PM
    • Replies: 0
    • Views: 3,792
    10-16-2011, 06:10 PM Go to last post
  28. Basic experiment - how to proceed with analysing data

    Hi, im trying to analyse some data from an experiment and I’m getting really confused about how I should proceed…... This whole experiment will...

    Started by kalamity‎, 10-15-2011 01:56 PM
    • Replies: 2
    • Views: 2,897
    10-15-2011, 09:54 PM Go to last post
  29. Is the following testable? I think so and have chosen Friedmans test, is it correct?

    Hello TS people, Thanks for talking a look at my question/problem, I am new, you can check out my introduction topic on the appropriate forum. ...

    Started by Samuel John Waldron‎, 10-13-2011 04:09 AM
    amova, experimental design, friedman test, repeated measures
    • Replies: 1
    • Views: 1,645
    10-13-2011, 12:46 PM Go to last post
  30. Mixed effects model, Mixed design ANOVA, split-plot group-by-time randomized design

    Are they the same thing? :confused: I just confused with the difference between "miexed effects model" and "mixed design ANOVA."

    Started by jerryno34‎, 10-12-2011 10:40 PM
    • Replies: 0
    • Views: 2,376
    10-12-2011, 10:40 PM Go to last post
  31. Cool Using Phylosor or Unifrac to find phylogenetic diversity with R

    Hi! I have created a presence/absence matrix and phylogenetic tree. As I understand it, phylosor requires these two files to run an analysis. I have...

    Started by Darkcraft‎, 10-11-2011 10:16 AM
    phylogenetic diversity, phylosor, picante, unifrac
    • Replies: 3
    • Views: 4,607
    10-11-2011, 10:52 AM Go to last post
  32. Exclamation Biostatistican needed for 24 month contract

    Biostatistician needed for a 24 month contract based in Germany. Looking for a candidate with experience in international clinical development of...

    Started by soniaw‎, 10-11-2011 05:17 AM
    • Replies: 0
    • Views: 1,416
    10-11-2011, 05:17 AM Go to last post
  33. Technical and Biological Replicates T-Test

    Hi! I have a question concering t tests. I did an experiment and compared 3 ( one control strain and 2 production strains) different strains and...

    Started by isomer‎, 09-20-2011 09:48 AM
    • Replies: 1
    • Views: 5,916
    10-10-2011, 12:51 PM Go to last post
  34. correlations between three dichotomous variables.

    I have three variables all of which are binary/dichotomous. For simplicity's sake let's say the variables are all whether a person buys a red car or...

    Started by blowe46‎, 10-07-2011 03:49 PM
    • Replies: 0
    • Views: 2,250
    10-07-2011, 03:49 PM Go to last post
  35. Survival Analysis: Is Cumulative Log Hazard the same as Complementary Log Log?

    Dear statisticians, Just wondering if Cumulative Log Hazard(CLH) is same thing as Complementary Log Log (cloglog) function? I am using R to...

    Started by ledzep‎, 10-05-2011 05:37 AM
    • Replies: 3
    • Views: 6,767
    10-07-2011, 11:10 AM Go to last post
  36. Winbugs starting

    hi I m working with health economic firm i just wanted to know that how to start learning about WINBugs software Thanks in anticipation

    Started by Mandy‎, 10-06-2011 10:24 AM
    • Replies: 1
    • Views: 2,969
    10-06-2011, 12:00 PM Go to last post
  37. 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: 14,239
    10-04-2011, 01:41 PM Go to last post
  38. hello please help this is urgent

    hello..i have a problem, my thesis adviser asks me to compute for parameter estimates in cox proportional hazards regression..I'm looking for a...

    Started by Khian Jane‎, 10-03-2011 06:47 AM
    • Replies: 3
    • Views: 2,523
    10-03-2011, 07:51 PM Go to last post
  39. Question Repeated measurments and destructive sampling

    Hi everyone I have done an experiment which investigated plant growth under three different parasite exposures (control, low + high; n=60). Some...

    Started by CWS‎, 09-26-2011 07:55 PM
    • Replies: 2
    • Views: 2,519
    10-03-2011, 04:39 PM Go to last post
  40. How to analyze treatment effects on continuous variables when follow-up time varies

    Hello to everybody! I am processing the data from a prospective study on patients that have been divided into two groups depending on whether they...

    Started by Uptitrate‎, 09-21-2011 11:52 AM
    • Replies: 3
    • Views: 3,555
    10-03-2011, 02:21 PM Go to last post
  41. 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: 10,106
    09-25-2011, 08:46 PM Go to last post
  42. Shared variance across hemispheres of the brain

    Hello, I'm in the process of doing some data analysis for an MRI project I've been working on in clinical neuroscience. I'll try to lay out my...

    Started by 01kolasj‎, 09-03-2011 04:30 PM
    • Replies: 4
    • Views: 3,644
    09-24-2011, 05:56 PM Go to last post
  43. interpretation of proc glm

    Hello I am using proc glm is SAS to run models. I am not finding any significance to conclude that my dependent variable is significantly...

    Started by praj‎, 09-20-2011 03:18 PM
    • Replies: 1
    • Views: 4,174
    09-20-2011, 04:47 PM Go to last post
  44. Mantel test, Arlequin and Fsts

    Hi, I am trying to figure out how to carry out a Mantel test and need some advice on which software to use and the type of input files...(at the...

    Started by imstuck‎, 09-20-2011 09:55 AM
    arlequin, correlation, fst, mantel test
    • Replies: 0
    • Views: 5,631
    09-20-2011, 09:55 AM Go to last post
  45. A cohort clinical trial?! Does it really exist?

    I saw a study which meets the criteria for a cohort study (without a control though) but it reads a cohort clinical trial! Can you tell me is it...

    Started by victorxstc‎, 09-18-2011 08:47 AM
    • Replies: 1
    • Views: 1,719
    09-19-2011, 07:48 PM Go to last post
  46. About Confidence Interval

    I have done frequency analysis using spss and now person is asking CI How to find CI

    Started by tpachhai‎, 09-09-2011 07:35 AM
    • Replies: 1
    • Views: 1,913
    09-15-2011, 03:23 AM Go to last post
  47. False Discovery Rate

    Hi, Anyone hear familiar with the FDR ? I have a sample of 80 people, some ill, some healthy. For each one I have a series of let's say for the...

    Started by NN_STAT‎, 09-13-2011 06:55 AM
    • Replies: 4
    • Views: 6,072
    09-14-2011, 08:04 AM Go to last post
  48. Unhappy error on blocking in RCBD

    We conducted a trial using a RCBD in a field we didn't have much information. We realized at the end of the experiment that we were wrong on the...

    Started by GastonDI‎, 09-12-2011 06:28 AM
    • Replies: 0
    • Views: 1,763
    09-12-2011, 06:28 AM Go to last post
  49. handling log(0) in log-likelihood calculations

    I wonder if anyone can help me with a vexing issue? How are undefined values handled in a log-likelihood calculation. If an observation yi from a...

    Started by rob c‎, 08-30-2011 05:46 AM
    • Replies: 2
    • Views: 6,891
    09-11-2011, 07:51 PM Go to last post
  50. Smile Confused about which test to use?!

    Hi, I am not the greatest when it comes to statistics so would appreciate someones opinion on the following!:confused: I have calculated...

    Started by imstuck‎, 09-09-2011 05:32 AM
    exons, gene diversity, nucleotide diversity
    • Replies: 0
    • Views: 1,975
    09-09-2011, 05:32 AM Go to last post
  51. Unblinding Concern: Projecting Last Event in > 2 Arm Study....

    In a two arm time to event study one can use various blinded projection methods using the aggregate event rate to estimate when the last event may...

    Started by betjoshua‎, 09-02-2011 09:29 PM
    event rate, projection, sample size determination, time to event, unblinding
    • Replies: 0
    • Views: 2,515
    09-02-2011, 09:29 PM Go to last post
  52. a simple question

    Hi, As you can tell I am statistically challenged. Suppose x and y are continuous, independent variables that represent traits of the N subjects...

    Started by danb‎, 08-28-2011 09:02 PM
    • Replies: 2
    • Views: 2,072
    08-29-2011, 01:46 PM Go to last post
  53. Error Bars (Sample size variation issues!)

    Hi! I have done an experiment with a plant species, seeing how survival rate changes with drying time (0, 1, 2 and 3hours). I repeated my...

    Started by efj500‎, 08-28-2011 06:02 AM
    • Replies: 14
    • Views: 4,092
    08-29-2011, 11:32 AM Go to last post
  54. Paired T-test?

    Hello, I have quantified immunostaining in tissue sections composed of 2 different cells types. I want to report the % increase or decrease in...

    Started by Critter‎, 08-26-2011 05:00 PM
    • Replies: 2
    • Views: 3,038
    08-29-2011, 11:07 AM Go to last post
  55. p for trend using SPSS?! anyone?

    hello kind people of the biostatistics forum, i would be ever grateful if anyone could help me with an urgent issue- i need to analyze data and...

    Started by naomi fliss isakov‎, 08-26-2011 05:51 AM
    • Replies: 0
    • Views: 3,315
    08-26-2011, 05:51 AM Go to last post
  56. Bone movement vs soft tissue movement

    Hello all, I'm a Dr. in England trying to work out which statistical test to use for some research. I have a group of 14 patients who underwent an...

    Started by WilliamBreakey‎, 08-21-2011 01:51 PM
    • Replies: 3
    • Views: 3,824
    08-23-2011, 11:57 AM Go to last post
  57. fixed effect with ancova

    Hi all, I need calculate fixed effect with ancova analysis (spss or genstat). My experiment was on fishes growth with differents diets (8): 15...

    Started by Rodrigo Badilla Cabrera‎, 08-16-2011 07:38 PM
    ancova, fixed effect
    • Replies: 1
    • Views: 2,198
    08-22-2011, 07:51 AM Go to last post
  58. SNPs Pvalue significance

    Hi all I am new to this forum and to the statistics world, so please bear with me :) There are: 453 controls 339 cases They are all...

    Started by zx8754‎, 08-22-2011 07:08 AM
    snps snp pvalue sample
    • Replies: 0
    • Views: 2,113
    08-22-2011, 07:08 AM Go to last post
  59. Logistic Regression and MLE

    Hello, I ran a logistic regression model. This model is based on maximum likelihood estimation. Now I need to explain it to my boss, who is not a...

    Started by WeeG‎, 08-18-2011 01:33 PM
    • Replies: 8
    • Views: 4,663
    08-21-2011, 01:04 AM Go to last post
  60. Two simple stat problems

    Hi, There are two stat problems. I would like to know if my answer and concept are correct. Problem1: In the sample size paragraph of their...

    Started by Jason‎, 08-17-2011 06:58 PM
    • Replies: 0
    • Views: 2,306
    08-17-2011, 06:58 PM Go to last post

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