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Forum: Biostatistics

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

  1. Parametric or Non-Parametric and why?

    I want to examine how three different treatments impact cytokine production in primary human cells (n=3) compared to an untreated control (example...

    Started by A.B‎, Today 02:41 AM
    • Replies: 9
    • Views: 162
    Today, 01:20 PM Go to last post
  2. Longitudinal analysis

    I am reading a book on medical analysis using SAS. These questions relate to longitudinal analysis. During a signficant section of the book they use...

    Started by noetsi‎, 09-19-2014 12:52 PM
    • Replies: 8
    • Views: 172
    Today, 10:34 AM Go to last post
  3. Hierarchical Spatio-temporal modelling

    Is it possible to create a hierarchical spatio-temporal model in a case whereby the age specific population size is not available at any given time...

    Started by juma‎, Today 07:59 AM
    • Replies: 0
    • Views: 36
    Today, 07:59 AM Go to last post
  4. Measuring variability within a system

    Does anyone know of a way to measure the amount of variability within a system to create a "metric" of variability that can then be used in a...

    Started by Austin‎, Yesterday 07:35 PM
    • Replies: 0
    • Views: 86
    Yesterday, 07:35 PM Go to last post
  5. applaying animal behavior algorithms in social science

    Dear Forum, I was hoping that someone could point me in the right direction; a starting point is all I need: In my dissertation I would like to...

    Started by MPtheR‎, 09-16-2014 11:35 PM
    algorithms, social sciences
    • Replies: 2
    • Views: 211
    09-20-2014, 12:28 AM Go to last post
  6. Biometrics

    Average height of tree is 23,2 m with standard deviation of 4,1 m. Draw and calculate above what height is the 10% of the highest trees? Heights are...

    Started by jerdnalesik‎, 09-18-2014 07:54 PM
    • Replies: 1
    • Views: 118
    09-18-2014, 08:01 PM Go to last post
  7. ANOVA on paired data

    Hello all, I am trying to design an experiment, and in order to dig a sample size I need to know how the data will be analyzed. This is an...

    Started by NN_STAT‎, 09-18-2014 03:22 AM
    • Replies: 0
    • Views: 117
    09-18-2014, 03:22 AM Go to last post
  8. Tobit regression output

    I ran a Tobit regression model looking at the effect of temperature, phosphorus and nitrogen and location on algae units (upper limit of 85 units)....

    Started by bugman‎, 09-15-2014 11:59 PM
    • Replies: 0
    • Views: 119
    09-15-2014, 11:59 PM Go to last post
  9. Unequal variances in ANOVA

    Non-statistician here, looking for help... My data (data from 8 different populations of plants) when analyzed using one-way ANOVA on SPSS v21...

    Started by huertaaj‎, 09-15-2014 01:24 PM
    one-way anova, unequal variances
    • Replies: 2
    • Views: 146
    09-15-2014, 02:44 PM Go to last post
  10. Relative risk

    The following comes from "Applied Medical Statistics Using SAS" 114-115. In it: p1 occurs when a disease is present when a risk factor is present...

    Started by noetsi‎, 09-11-2014 03:25 PM
    • Replies: 10
    • Views: 283
    09-15-2014, 10:36 AM Go to last post
  11. Does anyone know how to run log-rank test in R adjusting both Rho and gamma

    There used to be a package called surv2sample which is no longer supported by R.

    Started by joyrus‎, 09-13-2014 11:40 PM
    • Replies: 0
    • Views: 141
    09-13-2014, 11:40 PM Go to last post
  12. help with Kaplan-Meier curve

    I was trying to make a simple KM curve. The event is the death of cancer patients. The time is the time between diagnosis to last follow up. The...

    Started by sky_yin‎, 09-10-2014 12:33 PM
    • Replies: 0
    • Views: 104
    09-10-2014, 12:33 PM Go to last post
  13. Unclear output logistic regression

    Dear All, I performed a logistic regression with SPSS to determine which factors were associated with a binomial variable. Briefly, the binomial...

    Started by nicoladiggi‎, 09-08-2014 01:47 PM
    • Replies: 6
    • Views: 208
    09-10-2014, 08:51 AM Go to last post
  14. U shaped curve modelling

    Hello, Someone knows how to modelize and test a U shaped curve and if there is a specific procedure in SAS? Thanks for your help!

    Started by didye‎, 09-08-2014 11:48 AM
    u shape; model;
    • Replies: 2
    • Views: 113
    09-10-2014, 07:57 AM Go to last post
  15. Odds ratios lower than 1 for continous variable

    Lets says you want to check the effect of age on a specific event. In the univariate model : event = age, the odds is significantly lower than 1...

    Started by didye‎, 09-06-2014 05:16 PM
    average, odds ratio
    • Replies: 4
    • Views: 180
    09-07-2014, 12:47 PM Go to last post
  16. Help with power calculation!?

    Hi, I have a dataset on a cohort of patients with fixed number of subjects. I have a primary outcome and a primary exposure. If I want to do a...

    Started by leilafg‎, 09-01-2014 01:48 PM
    • Replies: 4
    • Views: 235
    09-04-2014, 04:48 PM Go to last post
  17. Comparing count data and cultivars in R

    Hi, I'm trying to analyse an experiment with this setup: A plant species with 16 different cultivars of 4-5 plants per cultivar (completely...

    Started by hobglobin‎, 09-03-2014 01:45 PM
    count data, glm, r code
    • Replies: 0
    • Views: 133
    09-03-2014, 01:45 PM Go to last post
  18. Incidence rate and Kaplan Meier

    Hello, I have a question about what we call "incidence rate" at the end of a longitudinal study. If there are a number of censored data, how do...

    Started by didye‎, 09-01-2014 08:24 AM
    incidence rate, kaplan-meier
    • Replies: 0
    • Views: 125
    09-01-2014, 08:24 AM Go to last post
  19. Is this possible?

    Hi, I have come stuck on a really simple question. I have access to excel and SPSS. I have a dataset of response to a treatment. Sample size =...

    Started by k093‎, 08-27-2014 10:49 PM
    • Replies: 7
    • Views: 316
    08-28-2014, 04:38 PM Go to last post
  20. 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: 0
    • Views: 166
    08-28-2014, 12:52 PM Go to last post
  21. When to use validation and derivation cohort?

    Hi everyone, I was wondering if there is any generic rules on when it's good to use a derivation and validation cohort on a dataset? So far I have...

    Started by dubaifrom‎, 08-28-2014 03:56 AM
    biostatistics, model checking, model validation, modeling techniques
    • Replies: 1
    • Views: 95
    08-28-2014, 08:00 AM Go to last post
  22. Unhappy Who to analyse these data please

    A very short question: I have a group of patients, followed after an operation, and I have collected a number of variables on these patients before...

    Started by Bio_Stat‎, 08-27-2014 10:51 AM
    • Replies: 2
    • Views: 172
    08-27-2014, 02:17 PM Go to last post
  23. comparing means when the control group has 2 subsets of data

    Hi there I have prospective study looking at functionality after an injury; let's say a big toe injury. I have the injured group (N=44) that has...

    Started by keamano‎, 08-25-2014 07:19 PM
    comparing means, multiple comparisons, propective clinical study
    • Replies: 2
    • Views: 180
    08-27-2014, 09:16 AM Go to last post
  24. calculation of sample size for different groups using proportions

    Dear all, kindly help me to arrive a sample population from each village in the study. i would like to do study survey in few villages and how...

    Started by karun sandeep‎, 08-25-2014 04:51 AM
    • Replies: 0
    • Views: 125
    08-25-2014, 04:51 AM Go to last post
  25. Kaplan Meier Curves + Cox PH

    Hi all: I'm doing a survival analysis on a dataset of about 650 cancer patients. The outcome is time to death. Patients are censored when they are...

    Started by jamesmartinn‎, 08-21-2014 07:42 AM
    • Replies: 3
    • Views: 211
    08-22-2014, 01:36 PM Go to last post
  26. not random but justified statistical methods for validating a diet quality index

    Has anyone good advice for validating a diet quality index? I have gone through validation studies and the methods used vary a lot. Some of them do...

    Started by Nutritionist‎, 08-20-2014 03:09 AM
    • Replies: 1
    • Views: 186
    08-20-2014, 09:13 AM Go to last post
  27. multi level categorical variable in a cox model

    Hello everyone, I would like to know which kind of test of significance do you use for categorical variables with more than two levels in a COX...

    Started by didye‎, 08-19-2014 06:39 AM
    categorical variable, cox model
    • Replies: 1
    • Views: 113
    08-19-2014, 07:58 AM Go to last post
  28. plots for hazard ratios / continuous variables

    Hello everyone, Somebody knows which kind of plots could I create to display a set of hazard ratios for continuous variables. I used to use...

    Started by didye‎, 08-18-2014 05:18 AM
    continuous variable, forest plot, hazard ratio
    • Replies: 1
    • Views: 118
    08-19-2014, 07:13 AM Go to last post
  29. Matching 3 groups

    Hello everybody! I have 3 treatment groups and I need to match them on several criteria. However, I don't know the steps to do that, should I...

    Started by abelstat‎, 08-19-2014 04:44 AM
    • Replies: 0
    • Views: 83
    08-19-2014, 04:44 AM Go to last post
  30. 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: 22
    • Views: 871
    08-19-2014, 02:51 AM Go to last post
  31. Interpretation of mixed model results

    Hello all, I need some assistance with interpreting the results of a mixed model and putting up textual conclusions. I ran a mixed model with a...

    Started by NN_STAT‎, 08-18-2014 08:05 AM
    • Replies: 0
    • Views: 102
    08-18-2014, 08:05 AM Go to last post
  32. Ordinal regression vs Chi-Square

    Hey guys, I've finished analyzing my data for an article regarding decompresion in divers. My dependent variable is ordinal - 1-no recovery...

    Started by XPeriment‎, 08-16-2014 04:50 AM
    • Replies: 9
    • Views: 243
    08-17-2014, 01:08 PM Go to last post
  33. 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: 9
    • Views: 405
    08-17-2014, 10:14 AM Go to last post
  34. Evaluating data via a three-way (2 x 3 x 4) ANCOVA

    Biomedical researcher here, trying to figure out how to analyze the results of a study on cell culture conditions. Three IVs were chosen: compound A...

    Started by lnhstats‎, 08-15-2014 09:47 AM
    ancova, control, interaction, prettest, timecourse
    • Replies: 6
    • Views: 308
    08-16-2014, 05:56 PM Go to last post
  35. Longitudinal analysis of drug use data

    Hi all, I'm looking to conduct a longitudinal analysis using data from 5 waves of an observational research study. What I'm really interested in...

    Started by omnibus‎, 08-14-2014 12:18 PM
    longitudinal data, modeling techniques, observational study
    • Replies: 4
    • Views: 173
    08-15-2014, 11:09 AM Go to last post
  36. non-comparative retrospective study: sample size calculation required?

    Hallo I am planning a very simple retrospective non-comparative study. The plan is to review patient charts of patients with cancer to determine...

    Started by noob‎, 08-13-2014 10:50 AM
    • Replies: 2
    • Views: 169
    08-15-2014, 05:49 AM Go to last post
  37. intertidal ecology - change in human use over two sampling periods

    Thank you in advance for any advice on this ecological study of human use of rocky intertidal habitats! I am examining the change in the number of...

    Started by intertidalecologist‎, 08-14-2014 04:48 PM
    • Replies: 0
    • Views: 147
    08-14-2014, 04:48 PM Go to last post
  38. DNA comparison: Repeated-measures ANOVA.. but too many parameters to consider?

    Dilemma about which test to correctly use... It's a tricky, confusing, one! I'm looking at DNA extraction methods, here's how I've got the data set...

    Started by Becky‎, 08-11-2014 06:22 AM
    anova, biology, multi, spss
    • Replies: 1
    • Views: 192
    08-14-2014, 10:14 AM Go to last post
  39. Longitudinal Adhesion Test for Patches

    Hello dear colleagues. I have to compare the adhesion of two drugs in the form of transdermal patches. According to EMA's (European Medicines...

    Started by lucasteixeira‎, 08-12-2014 09:35 AM
    longitudinal study, ordinal variable, statistical help
    • Replies: 0
    • Views: 125
    08-12-2014, 09:35 AM Go to last post
  40. Single cohort but comparing two groups WITHIN this cohort

    Hello, I have a single retrospective cohort that was selected over multiple years, without a control cohort (it is not possible to find a control...

    Started by theUmbra‎, 08-10-2014 01:33 PM
    • Replies: 0
    • Views: 105
    08-10-2014, 01:33 PM Go to last post
  41. Hopefully Simple Question: Two Way ANOVA or One-Way Repeated Measures?

    Hi all, I'm new here but have been wrestling with a statistical question for a while now, getting different answers depending who I ask. I'm really...

    Started by molbioadam‎, 08-05-2014 10:00 AM
    • Replies: 3
    • Views: 215
    08-09-2014, 08:31 AM Go to last post
  42. Multilevel Structure & Random Effects

    Hi! We have the following data structure and I'm wanting to get some feedback on how to correctly specify a multilevel model for research. ...

    Started by jamesmartinn‎, 08-05-2014 05:51 PM
    • Replies: 8
    • Views: 413
    08-08-2014, 11:14 AM Go to last post
  43. Classification model according to multivariate presence/absence dataset

    Hi there! I am currently working on the analysis of a two part experiment looking at bacterial communities in diatoms, under different...

    Started by stephiexoxo‎, 07-31-2014 03:06 AM
    classification, ecology, null distribution, presence/absence
    • Replies: 1
    • Views: 204
    07-31-2014, 05:52 PM Go to last post
  44. Response Rates

    Hello! I have a simple question. If I determined that I needed 100 participants to fill our my survey. We had a simple random sampling technique....

    Started by PsychStats_Leb‎, 07-31-2014 01:31 PM
    • Replies: 1
    • Views: 163
    07-31-2014, 03:06 PM Go to last post
  45. COX models and continuous variables

    Hello everyone. I have a simple and basic question about cox model. When I introduce a continuous variable in the model, the hazard ratio assessed...

    Started by didye‎, 07-30-2014 09:16 AM
    continuous variable, cox proportional hazard, survival analysis
    • Replies: 3
    • Views: 213
    07-30-2014, 10:44 AM Go to last post
  46. Required testing for complementary log-log-models

    Hello everybody, I am applying a complementary log-log-model (including time-invariant aswell as time-variant variables). So far I am not really...

    Started by geomo‎, 07-06-2014 07:24 AM
    • Replies: 1
    • Views: 214
    07-30-2014, 07:54 AM Go to last post
  47. non-parametric data for reference ranges

    Hello, I am very new to statistical analysis, but am very excited to to be learning it. I am working on finding reference ranges for some...

    Started by schmidlk‎, 07-28-2014 08:36 PM
    blood tests, medical statistics, new in the field, non-parametric, reference range
    • Replies: 0
    • Views: 166
    07-28-2014, 08:36 PM Go to last post
  48. Question How to interpret residual plot of a logistic regression?

    Hi all, I'm working on a default probability model and was modeling the default probability using logistic regression. The pearson residual and...

    Started by sufeipopo‎, 07-28-2014 02:55 PM
    • Replies: 1
    • Views: 278
    07-28-2014, 03:12 PM Go to last post
  49. Arrow Chi square: Goodness of fit and test of independence

    Ok, so Chi square GOF tests a variable for its fit to a theoretical proportion. Yet, a Chi test of independence does this, for two variables, with...

    Started by TheSloth‎, 07-27-2014 05:19 AM
    • Replies: 0
    • Views: 137
    07-27-2014, 05:19 AM Go to last post
  50. Statistical method to rule out cross-contamination?

    Hello, I hope there is someone who can help me find the right method for my needs. I have conducted a study in which I captured bees at several...

    Started by Bcentralis‎, 07-25-2014 03:32 PM
    • Replies: 0
    • Views: 159
    07-25-2014, 03:32 PM Go to last post
  51. 3D printing project + small sample size (5). How to analyze questionnaire data?

    Hi there, I am currently working on a research project investigating the use of 3D printed patient specific anatomy in pre-operative planning. The...

    Started by stanleyliew‎, 07-24-2014 04:54 PM
    • Replies: 0
    • Views: 221
    07-24-2014, 04:54 PM Go to last post
  52. including items in final version of new instrument

    I have 2 questions I would like advice on. They relate to a paper I'm reviewing for a journal. When developing a new instrument, if you do a...

    Started by MarcelProust‎, 07-22-2014 12:10 PM
    • Replies: 0
    • Views: 155
    07-22-2014, 12:10 PM Go to last post
  53. fish and seagrass help

    Hello, I'm doing something very similar with seagrass and bare sand substrates fish data and just wondering if you had any luck figuring out how to...

    Started by helbob‎, 07-18-2014 07:59 AM
    • Replies: 5
    • Views: 265
    07-21-2014, 06:04 AM Go to last post
  54. [SPSS] Comparison of Fish abundances over 3 inter-tidal zones and 4 sites.

    Hi there, I'm relatively new to statistical analysis so bare with me... I have a research project that aims to find whether fish species...

    Started by Shaan‎, 04-24-2014 08:32 AM
    • Replies: 2
    • Views: 370
    07-20-2014, 04:30 AM Go to last post
  55. Combining two ORs with the same control group

    Hi everybody. I am doing a meta-analysis of observational studies. As the disease I am working on has different stages, some of the studies reported...

    Started by amirh899‎, 07-16-2014 09:21 AM
    • Replies: 12
    • Views: 311
    07-17-2014, 01:19 PM Go to last post
  56. Correct Order in Repeated-Measures Design

    A group of 8 volunteers performed a task on two different devices and a particular variable was measured. The question to be answered is if there is...

    Started by DaDeKi‎, 07-13-2014 04:26 PM
    • Replies: 5
    • Views: 244
    07-17-2014, 09:48 AM Go to last post
  57. Randomized controlled trial sample size calculation

    Sorry if this is in the wrong thread. I am trying to determine if a research project is feasible to conduct by calculating the sample size needed. ...

    Started by efficientfuel‎, 07-16-2014 02:24 PM
    • Replies: 2
    • Views: 267
    07-16-2014, 04:29 PM Go to last post
  58. When do sample size calculations need to adjust for clustering?

    I am aware that sample size calculations for cluster RCTs must adjust for clustered data. I would like to understand better if such adjustment might...

    Started by mayiara‎, 07-14-2014 04:53 PM
    clustering, power, sample size calculation
    • Replies: 1
    • Views: 237
    07-15-2014, 01:53 AM Go to last post
  59. Relationship Satisfaction short Study participants wanted -

    You must be in a relationship to participate in these studies. You can be anywhere on the planet. This preliminary study should only take anyone a...

    Started by williamsven‎, 07-14-2014 10:44 AM
    • Replies: 0
    • Views: 185
    07-14-2014, 10:44 AM Go to last post
  60. which statistic test should I use

    Hello, I have a problem in picking the right statistic test in my case. I have analyzed the microbial community in one sample with different methods,...

    Started by rigel‎, 07-13-2014 12:26 AM
    • Replies: 0
    • Views: 229
    07-13-2014, 12:26 AM Go to last post

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