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# Forum: Biostatistics

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

1. ### separate a population into groups using 3 sets of data at once

Hi there, I'm working on a population for which I have done 3 chemical analyses that give the concentration of different products in their tissues....

• Replies: 2
• Views: 1,163
06-16-2015, 12:04 PM
2. ### Confidence interval for person time incidence rate

Dear everyone, I would like to estimate a 95%CI of person time incidence rate (as 45 death per 10,000 person year) Anyone knows a way to estimate...

• Replies: 2
• Views: 1,678
06-15-2015, 02:41 PM
3. ### Correlating bird diversity with sampled parameters like area size, elevation R-studio

For my thesis I need to find the connection between bird diversity and a bunch of parameters we recorded in the field for each locality. The recorded...

• Replies: 0
• Views: 1,394
06-13-2015, 05:41 AM
4. ### Power and Sample Size Calculation

Hi, First post here--i'm having trouble figuring out how to calculate the sample size for a study I'm planning. I don't have much statistics...

• Replies: 2
• Views: 2,214
06-12-2015, 07:28 PM
5. ### how to analyse 28 blood parameters in 3 stages of the disease ?

hello, I would like to do an analysis of 28 blood parameters in 3 stages of the disease all parameters have specific numerical values I have...

• Replies: 0
• Views: 1,115
06-12-2015, 05:02 PM
6. ### No Wald Chi2 or Prob > Chi2 value generated for logistic regression?

I am trying to run a logistic regression analysis using STATA and get the following output: Why is no value generated for my Wald Chi2 and Prob >...

• Replies: 3
• Views: 2,581
06-11-2015, 02:12 AM
7. ### How to incorporate data from a previous trial

Can I incorporate data from a previous trial in a new trial without any adjustment for bias (individual subject data)? If not, which is the best...

• Replies: 0
• Views: 734
06-10-2015, 06:45 AM
8. ### Power calculation

I am working on a study that aims to assess predictors of insufficient food intake among elderly patients. In the study I am evaluating (9)...

• Replies: 0
• Views: 846
06-09-2015, 10:19 AM
9. ### Incidence rate in a cohort with small sample size

I have a small cohort of people with a specific disease (n=300) and studying the incidence of a related disease (which is kind of rare and normally...

• Replies: 5
• Views: 1,704
06-08-2015, 01:17 PM
10. ### Basic help with stats for drug treatments

Hi there :wave: So I haven't a clue where to start and am hoping someone on here can point me in the right direction. I'm starting to analyse my...

• Replies: 1
• Views: 1,610
06-08-2015, 11:06 AM
11. ### Removing Batch Effects (with svaseq and Combat)

Hi everyone ! :) I'm a french student, so sorry in advance for my english... I'll try to do my best :). I currently work on a data set with a...

• Replies: 0
• Views: 2,968
06-07-2015, 02:48 AM
12. ### Help with glm--- Simple Logistic Regression

Hi All! Thanks for reading. I wanted to compare month of sample collection (April, May, June, and July) to presence/absence data (coded in binary...

• Replies: 1
• Views: 1,370
06-06-2015, 01:25 PM
13. ### interpreting logistic regression in case p=0.0 and/or p=1.0

Hi there, I have this (fake) example: case yes no a 25 1 b 30 0 c 0 20 I want to compare the percent of "yes" in the...

• Replies: 0
• Views: 1,095
06-04-2015, 04:23 AM
14. ### KM curve

Hi all, If I have a KM curve (survival vs years) and I have the number at risk each year (as well as hazard ratio for death over a median follow up...

• Replies: 3
• Views: 2,171
06-03-2015, 09:48 PM
15. ### Presence/absence multivariate data

Hi, I'm trying to analyse some data I've gathered from some fossils. I have about 40 different specimens and for each specimen I've recorded the...

• Replies: 0
• Views: 3,892
06-03-2015, 12:54 PM
16. ### help with comparing paired values

Hi I have a question regarding comparing data. I have data in spss as presented here:...the list goes on for a thousand entries (ie...A, B, C, D,...

• Replies: 2
• Views: 1,781
06-02-2015, 03:55 PM
17. ### Comparing categorical outcome variables in repeated measures design

I am working on an observational prospective longitudinal study with a repeated measures design. The same categorical outcome is measured for five...

• Replies: 0
• Views: 1,369
06-02-2015, 03:19 PM
18. ### Comparing proportion between categorical outcome variables, repeated measures design

I am working on an observational prospective longitudinal study with a repeated measures design. The same categorical outcome is measured for five...

• Replies: 0
• Views: 1,145
06-02-2015, 03:15 PM
19. ### How do we avoid pseudoreplication while examining stickleback-gender in perch stomach

We are working on a project were the sex of sticklebacks in perch stomachs are assesed. The question here is; how do we avoid pseudoreplication? We...

• Replies: 0
• Views: 1,632
05-29-2015, 06:15 AM
20. ### Probability of association in binary variables (allergy dataset)

Hi I am an MD analyzing a series of patients who have undergone allergy testing. For each patient (20000 in total), there are 40 tested allergens...

• Replies: 1
• Views: 1,790
05-26-2015, 06:17 AM
21. ### Dealing with multiple confounding variables

for example, we have 3 confounding random variables, x1, x2 and x3 with 3 different variances. If we had to treat each variable alone, we would have...

• Replies: 3
• Views: 1,651
05-24-2015, 06:24 AM
22. ### logistic regression versus PCA

I am doing a retrospective research on breast cancer using multivariate estimates. The aim of the research is to calculate the probability of finding...

• Replies: 0
• Views: 1,669
05-20-2015, 08:52 PM
23. ### Adjustment for Odds Ratios

At present, I am working on a meta-analysis that observes the effect of physical activity for a disease (i.e. cancer). For each study we have used...

• Replies: 10
• Views: 2,031
jle
05-17-2015, 09:31 PM
24. ### Normal versus non-normal - presentation of results in publication

Dear all Can anyone help me with the following question: I have a outcome variable that is compared for different grouping variables. For some of...

• Replies: 3
• Views: 862
05-14-2015, 08:49 AM
25. ### Adjustment for confounders for testing equality of variance

Dear all I wonder if there is a method that allows to adjust for confounding variables when testing for the equality of variances. I am comparing...

• Replies: 1
• Views: 1,162
05-14-2015, 05:33 AM
26. ### Kruskall-Wallis/Dunn or Mann-Whitney to compare communities along an area?

Hi, I would like to know your opinion about the best statistical approach to use in the following case: - 10 sampling points distributed along an...

• Replies: 0
• Views: 984
05-12-2015, 04:34 AM
27. ### Comparing groups/sites---need advice identifying variables and appropriate tests

Hi, thank you for reading this and your potential input. This is a research study. I examined the prevalence of parasites in one insect species...

• Replies: 0
• Views: 945
05-11-2015, 03:54 PM
28. ### Paired or unpaired data and questions about test with >2 groups

Hi guys! I am here for some help with my statistics. I am currently working on a small project involving the expression of surface markers on cells...

• Replies: 2
• Views: 1,104
05-10-2015, 04:15 PM
29. ### Wilcoxon test for statistical significance

Hi guys, I have a simple question (sry for the probably imprecise formulation, I never went to a statistics class) Assume we have a population...

• Replies: 5
• Views: 1,429
05-05-2015, 04:23 PM
30. ### Goodness of Fit of Time Series Prediction

I am an academic neuroscientist working on the following project: I am attempting to determine the evoked response of a sensory nerve (time series in...

• Replies: 0
• Views: 1,168
05-05-2015, 10:07 AM
31. ### Significance testing among groups of time series data

I have produced 2 groups of time series data. Each group contains 100 time series, each of which is a solution to an ordinary differential equation...

• Replies: 1
• Views: 1,641
05-05-2015, 09:39 AM
32. ### Comparing Treatments for Spinal Cord Injury

Hi Guys. First post in this forum (actually, in any statistics forum). I am not from an English speaking country, so you may find some grammatical...

• Replies: 4
• Views: 1,469
05-04-2015, 09:26 AM
33. ### ROC curve after logistic

Hello all. I have a dataset of around 700 subjects. I wanted to test whether the blood values of a protein are associated to a certain disease and...

• Replies: 1
• Views: 919
05-03-2015, 01:05 PM
34. ### Making sense of the directionality parameter

Hello, This post has been cross-posted here. I fail to delete the current post to leave only the other post open. Feel free to delete this post if...

• Replies: 0
• Views: 1,363
05-03-2015, 11:52 AM
35. ### Comparing the Power and Effect Size from Different Studies

Hi there Talk Stats Community, I am an undergraduate research assistant. Currently I am doing research on a project, and our results have...

• Replies: 0
• Views: 1,355
05-02-2015, 12:21 AM
36. ### Calculate Incidence rate for disease with fertility/mortality data

I am trying to calculate disease incidence in a certain country. I have the number of cases detected over 10 year period. The disease affects...

• Replies: 2
• Views: 1,534
05-01-2015, 12:29 PM
37. ### One sample study design - Multivariate methods?

Good Day, I am planning a one sample study of 230 patients. I am thinking of using the one sample t-test and the binomial test to perform...

• Replies: 5
• Views: 1,666
04-28-2015, 01:15 PM
38. ### How to compare samples of different sizes to look for a correlation

Hello :) I'm hoping to find somebody that can give me some advice with my Statistics. I carried out a study on birds diet. My results show...

• Replies: 0
• Views: 1,032
04-26-2015, 03:54 PM
39. ### How to estimate transition probabilities in the absence of individual patient data?

What I tried so far is to read of the survival curves given in clinical trials with Plot Digitizer, with months ((t)months) as the X axis and...

• Replies: 0
• Views: 1,178
04-25-2015, 11:22 AM
40. ### Dunn's Multiple Comparison Test - Graphpad

Hey, So I worked with non-parametric data (more than 3 groups) so I did the Kruskal-Wallis test to compare these groups. To see which group...

• Replies: 0
• Views: 2,139
04-25-2015, 03:37 AM
41. ### biological relevance of low fold changes in gene/protein expression?

Hello, I have proteomic data pertaining to organs of rats treated chronically with a low dose of a chemical. The rats have developed pathologies...

• Replies: 0
• Views: 1,228
04-22-2015, 11:21 AM
42. ### Spearmans Correlation Doubt

Hello! I have some doubts about Spearmans's Correlation and I would like to ask your help! I have 5 variables (3 independent and 2 dependent) and...

• Replies: 1
• Views: 1,608
04-17-2015, 03:44 PM
43. ### Can subject be a factor?

Let's say we have an epidemiology research with 5 subjects (for simplicity): John, Mike, Andy, Frank and Philip. They contacted meningitis and their...

• Replies: 2
• Views: 1,166
04-15-2015, 11:52 AM
44. ### what to do with duplicate subjects in data set

I have 2 subjects in my data set that I suspect are duplicates-also the data is highly unusual, do I exclude then from analysis? According to the...

• Replies: 1
• Views: 1,532
04-12-2015, 08:53 PM
45. ### pairwise associations-which model to run?

Should I perform multiple linear regression for the following homework question? Perform the necessary analyses for creating “Table Q1: Pairwise...

• Replies: 0
• Views: 1,183
04-12-2015, 04:29 PM
46. ### weighting of aligned subsequences by their length

I have a pool of subsequences, each one associated with a probability (and other properties that you don't need to know) that quantifies how...

• Replies: 0
• Views: 1,108
04-11-2015, 10:13 AM
47. ### Taking the Mean of a Mean

Hello, I have 2 groups, each with 3 subjects and each subject with 5 replicate values. I want to compare the means of the measured values between...

• Replies: 0
• Views: 1,456
04-10-2015, 11:28 AM
48. ### How to format a null hypothesis without statistical analysis

I had to complete a research project that involved a cell membrane protein, and I had to find if there was a correlation to its presence on cells and...

• Replies: 1
• Views: 1,165
04-09-2015, 01:34 PM
49. ### How to compare IRRs of two different groups?

Hello all, thanks in advance for your help. This is my question: I have a structured panel data for repeated measure over time per single person ...

• Replies: 3
• Views: 2,268
04-09-2015, 11:45 AM
50. ### How to analyze my longitudinal data

Hi all, I've been struggling to figure out the best way to analyze my data. I randomized participants to one of 3 groups and had them complete my...

• Replies: 2
• Views: 1,420
04-08-2015, 01:58 PM
51. ### Cox regression application in business/finance

Hi all, I hope this is the right forum to ask as cox regression is usually use by bio-statisticians. My research is about companies which...

• Replies: 4
• Views: 2,936
04-07-2015, 10:29 PM
52. ### 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...

• Replies: 1
• Views: 1,542
04-07-2015, 10:12 AM
53. ### Multiple imputation and ROC curve anlaysis

Hi, I have searched extensively for a solution to the following problem, without success. I have used multiple imputation on SPSS 22 to create 5...

• Replies: 9
• Views: 8,830
04-02-2015, 12:36 PM

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