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# Forum: Biostatistics

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

1. ### Ecology : re-group samples based on distance measure

Hello, Good morning TalkStat Forum, hedre is my question of the day :) I have an ecological matrix of samples (rows) X species abundance...

• Replies: 4
• Views: 2,667
07-02-2013, 07:13 AM
2. ### Choosing a sample size for a pilot study

I am trying to figure out how to compute a sample size. Since this is a pilot scale study the results will likely not be definitive, but I want to...

• Replies: 18
• Views: 10,026
07-01-2013, 09:52 AM
3. ### comparing the frequency use of vocabulary between two sign languages

I am comparing the vocabulary of two sign languages in two locations to see if the vocabulary use in statistically different between locations. The...

• Replies: 0
• Views: 1,938
06-30-2013, 09:09 PM
4. ### testing a prognostic score

Hi, can anyone please help me? I have to see to how a prognostic score correlates with patients' evolution, and by that I mean: mortality, days of...

• Replies: 5
• Views: 2,231
06-30-2013, 08:12 PM
5. ### Comparing a continuous variable vs a continuous and a nominal

Hi. I'm studying the effect of hummingbird feeders on the hummingbirds' pollinization function. We counted the amount of birds feeding on artificial...

• Replies: 0
• Views: 1,412
06-27-2013, 12:26 PM
6. ### PCA for identifying bacteria species & concentration

Hi all, For an experiment I'm trying to see whether I can distinguish bacteria species and concentration using fluorescence, and I'm stuck on...

• Replies: 3
• Views: 3,306
06-27-2013, 10:41 AM
7. ### area under the ROC curve for a cutoff point

I kindly requested help about a study of mine concerning ROC curve analysis in medical diagnosis. I use R software programme to find optimal...

• Replies: 2
• Views: 4,702
06-26-2013, 02:36 AM
8. ### Significant differences in significant differances

Hello forum Gurus, I have tried search for a problem similar to mine in these forum to no avail. So here goes. I have 4 groups (A,B,C,D)...

• Replies: 3
• Views: 1,821
06-25-2013, 03:10 PM
9. ### Interrupted time series analysis with comparison group

Hi, I was wondering if you could provide some guidance with regards to study design and the statistical analysis i should use for a pilot study we...

• Replies: 0
• Views: 2,951
06-24-2013, 06:29 PM
10. ### "As treated" analysis, fixed cohort analysis, and NNH?

I had a few questions in regards to this study: http://www.bmj.com/content/346/bmj.f880.pdf%2Bhtml They conducted an "as treated" analysis and...

• Replies: 0
• Views: 2,745
06-23-2013, 09:50 PM
11. ### Paired or Unpaired t Test

Hi, I am working on a project in which we are comparing data about two groups of patients: the experimental group of 12 patients who received a...

• Replies: 2
• Views: 2,723
06-22-2013, 09:07 PM
12. ### Which programming language/database to learn?

I'm interested in pursuing a career in biostatistics, and I'm wondering which language/database will be useful in the field of...

• Replies: 0
• Views: 1,545
06-20-2013, 10:54 PM
13. ### Appropriate tests for experimental crab growth and survival research

Hi, I would like to know which test(s) would be most appropriate to analyze my data. I conducted an experiment with crabs to assess the effects...

• Replies: 1
• Views: 1,343
06-20-2013, 03:18 PM
14. ### GLMM Predictor variables

Hi all, I have a quick question regarding predictor variables in a GLMM analysis, a subject I am new to. I am running a study investigating...

• Replies: 0
• Views: 1,285
06-20-2013, 05:31 AM
15. ### Accounting for demographics when outcome is rates

Hello, I've been reading some public health papers and they account for demographic factors such as age, gender, and race in regression models...

• Replies: 7
• Views: 2,176
06-19-2013, 03:15 PM
16. ### Calculating effect size for a within group comparison of score before&after treatment

Hi all, :wave: I am wondering which formula will be more suitable for calculating effect size (Cohen's d) of an intervention with scores obtained...

• Replies: 0
• Views: 2,726
06-18-2013, 10:34 PM
17. ### calculation of relative risk.

..........................Smokers...................Non- Smokers Iron Exopsure.......+..........-...................+..........- Lung...

• Replies: 3
• Views: 1,930
06-18-2013, 09:31 AM
18. ### How to assess a new diagnostic test apart from ROC

I have a diagnostic scoring system that uses 6 variables, each an ordinal or dichotomous value (some 0 to 1, others 0 to 4) (that when summed...

• Replies: 2
• Views: 1,919
TS1
06-14-2013, 12:14 PM
19. ### multicenter designs and power analysis

Hello all, I am designing a study for examining the efficacy of a new treatment vs. a standard of care. For simplicity, let's say that my outcome...

• Replies: 3
• Views: 1,592
06-13-2013, 07:53 PM
20. ### likelihood of false positive in Robust regression model. Gene expression results

:shakehead Hi I'd like to calculate the probability of a gene A or genes A , B, C and D occuring due to chance alone in a genelist of concordant...

• Replies: 0
• Views: 1,095
06-13-2013, 08:05 AM
21. ### SEM of 3 independent experiments

Hi all... It's my first time to post in this forum. I would like to calculate the standard error of mean (SEM) of 3 independent experiments. ...

• Replies: 1
• Views: 2,748
06-12-2013, 09:46 PM
22. ### Ecological changes in echinoderm populations: what statistical model is appropriate

Hi Talk Stats and associated folks We are doing an ecological study on the effects of removal of an invasive seastar (Asterias amurensis) from...

• Replies: 7
• Views: 2,595
06-12-2013, 09:43 PM
23. ### How to build a regression model of survival data ?

I would like to predict the response variable using different predictors. So far I have been working with multiple linear regression. However as my...

• Replies: 1
• Views: 1,889
06-12-2013, 09:40 PM
24. ### What test to use?

Hello everyone I need some help with a statistical analysis of two groups of time variables. So i have an unequal sample size with about 50...

• Replies: 1
• Views: 1,124
06-12-2013, 09:13 PM
25. ### Reducing likert-type scales from 10 point scale to lower order point scal

Have made lots of movement in looking at this project... Overall Aim: To construct a clinical medical image scales (10 images in scale)...

• Replies: 0
• Views: 2,138
06-12-2013, 06:53 PM
26. ### association of binary data with multidimensional scaling?

Hi everyone, I have 10 binary variables, each coding the presence or absence of an event for each of 2000 participants in the study. I would like...

• Replies: 3
• Views: 3,579
06-12-2013, 06:27 PM
27. ### Partial least squares regression with categorical variables?

Hello, This is similar to a recent post about SNP data. I have genotype data based on SNPs (single nucleotide polymorphisms) for ~300 genetic...

• Replies: 1
• Views: 5,838
06-12-2013, 02:13 PM
28. ### Appropriate tests for comparing 2 normally distributed datasets (ttest?)

Hello, It's been a while since my A-level statistics course so I just want to make sure I'm doing the appropriate test for my data. I'm a PhD...

• Replies: 2
• Views: 1,642
06-12-2013, 08:23 AM
29. ### Percentages as a continuous variable

Hello all I have a variable, on a continuous scale, it is some medical value before getting a treatment. After the treatment, this value is being...

• Replies: 4
• Views: 2,523
06-12-2013, 01:55 AM
30. ### A better way to pick up on hidden variables

Hi, I'm trying to determine cattle disease risk through various values, including weight, through a machine learning application. I have the usual...

• Replies: 1
• Views: 1,484
06-12-2013, 12:30 AM
31. ### topics for thesis in phd

i am a phd student in biostatistics and i should choose a topic for my thesis but i am confused to choose a best topic. is any person to help me?

• Replies: 6
• Views: 1,701
06-09-2013, 12:36 PM
32. ### Survival Analysis (left censored data)

Hello everybody, this is a question about survival analysis and although it is about a management science topic, I think the methodology fits in...

• Replies: 0
• Views: 1,844
06-06-2013, 04:52 AM
33. ### Which analysis more suitable?

Dear all, My data consists of 8000 rows and 14 columns, as follows: The rows correspond to quadruplicate measurements of 2000 variables and columns...

• Replies: 1
• Views: 1,508
05-31-2013, 03:44 PM
34. ### Relative risk: lung cancer and smoking ! thanks in advance for your help

.........................Smokers...................Non- Smokers Iron Exopsure.......+..........-...................+..........- Lung...

• Replies: 3
• Views: 3,845
05-31-2013, 12:32 PM
35. ### Gehan-Breslow-Wilcoxon test or Cox regression

Hello, I am looking at the relatively small dataset and comparing the survival of 2 groups of mice. The end survival is not very difference but it...

• Replies: 0
• Views: 5,188
05-28-2013, 04:21 AM
36. ### Distribution of a subset of the complete sample

Dear all, My question can be easily misunderstood, so please allow me to briefly explain the experimental conditions. I have measured a...

• Replies: 4
• Views: 2,426
05-27-2013, 02:12 AM
37. ### Anova? Chi-square?

Hi, I've been asked to analyze some data and I wanted to get a second opinion on the way I plan to. I have a sample of 8000 teachers. For each...

• Replies: 4
• Views: 1,909
05-26-2013, 05:55 AM
38. ### t-test or ANOVA in a validationstudy?

Hello, i am doing reasearch for my bachelor thesis in physiotherapy and i need help with the statistics. my reasearch is about the validation of...

• Replies: 4
• Views: 1,529
05-25-2013, 04:28 AM
39. ### Multivariate regression

What is the most suitable way to assess the effect several independent ordinal variables have on a single nominal variable ? For example the...

• Replies: 2
• Views: 1,540
05-23-2013, 09:45 AM
40. ### Colinearity, Logistic GEE

Hi! I'm running a model and I think I've ran up against a colinearity issue. We have approximately 300,000 students in our dataset. For these...

• Replies: 1
• Views: 2,358
05-22-2013, 05:08 PM
41. ### Which stat? Difference of two means. T-test paired vs unpaired

Hi guys. I'm trying to determine if the difference between two groups of data are statistically significant. Looking at mri, I am measure the...

• Replies: 2
• Views: 3,206
05-22-2013, 09:51 AM
42. ### Which stat test to use

Hi all, I have a data set like this: Nematodes copepods Pylochaetes Controle1 1 ...

• Replies: 1
• Views: 1,375
05-17-2013, 05:55 AM
43. ### test to assess proportional difference over time between groups

I am trying to determine the appropriate test to run for a community-based intervention. There are 2 groups (intervention and control) and 2 time...

• Replies: 1
• Views: 1,887
05-16-2013, 08:20 PM
44. ### Correct assessment of the sampling distribution of the mean for my experiment?

Hi, all. I'm trying to properly analyze data from an experiment and could use some help bridging the mental gap between statistical theory (which I...

• Replies: 7
• Views: 2,645
05-15-2013, 06:21 PM
45. ### Enrichment analysis between two sets of proteins

I'm trying to calculate a statistical measure describing the overlap of two sets of proteins. The issue is that the sets are from different organisms...

• Replies: 5
• Views: 2,312
05-15-2013, 02:09 PM
46. ### Surgical Outcomes?

Does anyone know a good SSPS tutorial for the project I'm doing? I want to do a retrospective study to see if Drug A reduced postoperative...

• Replies: 2
• Views: 1,106
05-15-2013, 10:07 AM
47. ### How to estimate a population prevalence from several primary studies

I have received point estimates from several studies for the prevalence of a rare disease, and I would like to estimate the over-all prevalence in...

• Replies: 0
• Views: 1,189
05-15-2013, 02:30 AM
48. ### Site, treatment,numbers before and after

Hi I have data from an environmental experiment. We treated a section of river bed to remove an invasive species. I could do with some help...

• Replies: 3
• Views: 1,743
05-14-2013, 11:57 AM
49. ### Using a repeated measures, two-way ANOVA.

I want to compare the outcome of two different algorithms applied to one set of MRI images. Each MRI image will be manipulated twice. Once using the...

• Replies: 0
• Views: 1,974
05-12-2013, 03:58 PM
50. ### Causal inference and survival analysis coursework

Hey all, I'm an undergrad statistics student with an interest in causal inference topics such as propensity score analysis and instrument variable...

• Replies: 2
• Views: 1,923
05-09-2013, 04:05 PM
51. ### Correlation analysis

Hi, First I have to apologise for the probably stupid question, but my statistic knowledge is pretty much 0 and after searching for an answer for...

• Replies: 2
• Views: 1,850
05-09-2013, 03:05 PM
52. ### Survival analysis: how do i include a random effect and interval censoring?

Hi, I'm trying to use some form of survival analysis (e.g. accelerated failure time or proportional hazards) to study seed germination time. My...

• Replies: 0
• Views: 1,222
05-08-2013, 01:43 PM
53. ### Graphs, Funnel Plots, suggestions?

Hi! I'm trying to display some data, let me describe it to you. I have a group of about 5000 teachers. For each teacher, I have the rate of...

• Replies: 4
• Views: 1,975
05-07-2013, 12:54 PM
54. ### Incidence & competing risks

Hello, I'm a bit puzzled about competing risks. I've used competing risks methods (gray's test and fine and gray regression) a while ago, but...

• Replies: 0
• Views: 2,188
05-06-2013, 05:41 AM
55. ### how to test 2x2 table with an one empty cell in admission patients?

I am a clinician working for a community based hospital. A few days ago, my fellow doctor asked me if I could give some advice for her data. ...

• Replies: 1
• Views: 4,033
05-05-2013, 06:55 AM
56. ### How to normalize LC-MS data with minimum bias (proteomics)

Hello all, I'm working with quantification of some modified peptides enriched from serum of sick and healthy people. In the crude data (integrated...

• Replies: 8
• Views: 7,839
05-03-2013, 04:32 AM
57. ### Mean Residual Life

Hi, I've been tasked with solving the mean residual life given the density function f(x) and the survival function S(x) I think mean residual...

• Replies: 0
• Views: 1,635
05-01-2013, 02:00 PM
58. ### Survey

I'm a Biostatistician working for a researcher who wants to find out if length of training would affect peoples opinion in choosing a certain medical...

• Replies: 2
• Views: 1,740
05-01-2013, 12:38 PM

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