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# Forum: Biostatistics

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

1. ### Estimating main effects in a two factorial log linear model when applied to RNA-seq

Hi everybody, I'm going to apply multiDE, an R package for detection of DEG in multiple treatment conditions, on some RNA-seq time series data......

• Replies: 0
• Views: 188
09-16-2016, 02:29 PM
2. ### Survival analysis

Hi there, I am doing some breast cancer survival analysis on population-based registry data...I have outlined to estimate incidence trends and...

• Replies: 2
• Views: 167
09-16-2016, 04:20 AM
3. ### What test to use?

Hi all, I am new to statistics. Now, I am doing a research but I don't know which test to use. Basically, I have four groups with both positive...

• Replies: 1
• Views: 116
09-14-2016, 02:54 PM
4. ### R caret package: problems understanding the functions in confusionMatrix

Hey, I earlier posted about the problematic interpretation of PPV (positive predictive value). As there seems to be no easy solution for that I...

• Replies: 2
• Views: 211
09-13-2016, 01:44 AM
5. ### Analysing pre- and post-treatment lactate curves

Good morning all, Has anyone got experience with analysing lactate against power curves? I have pre- and post-treatment lactate curves for 10...

• Replies: 0
• Views: 77
09-12-2016, 03:21 AM
6. ### [SPSS - post hoc analysis and Logistic regression] When the result don't line up

I'm a medical student doing his research interneship. We're currently investigating if there's a link between motoric and mental outcome and MRI...

• Replies: 0
• Views: 146
09-08-2016, 05:34 AM
7. ### How to evaluate significance.

Hi, I have 58 samples and an enrichment analysis was done to each of them. So for each sample I have a list of enriched terms. I've collected the...

• Replies: 0
• Views: 152
09-06-2016, 11:14 AM
8. ### ROC curve cutoff not significant, but it works

I'm dealing with a numerical variable and its prognostic significance in a sample of cancer patients. I'm trying to find an optimal cutoff point for...

• Replies: 4
• Views: 291
09-04-2016, 01:14 PM
9. ### How to analyze this data

Hello, I need guidance in analyzing the outcome. I have 4 independent variables, and 2 dependent variables. The sample size is ~600. I...

• Replies: 1
• Views: 138
09-02-2016, 03:46 AM
10. ### Help deciding paired vs unpaired t-test

Hi, I am analyzing an experiment in which protein levels were examined in two different strains of bacteria. Lets call them A and B. Three...

• Replies: 2
• Views: 119
09-01-2016, 02:19 PM
11. ### Help decide on appropriate test for experiment design

Hello - new to the forums here! I work in cell biology and a colleague and I are designing an experiment to determine the appropriate...

• Replies: 5
• Views: 327
08-30-2016, 04:01 PM
12. ### Positive predictive value of biased data

Hey, I am currently dealing with prediction of binary data due to structural alerts. This means if a substructure is within the query structure it...

• Replies: 2
• Views: 139
08-30-2016, 01:21 AM
13. ### Matched Groups Statistics

Hello all hope this is the right thread for the question and that someone will be able to help me out :confused: I have created a propensity...

• Replies: 2
• Views: 133
08-29-2016, 01:42 PM
14. ### I need advice on Fisher's exact test

I recently submitted a paper and in my study, I wanted to see if there is an association between a gene mutation and the absence/presence of the...

• Replies: 4
• Views: 237
08-29-2016, 03:50 AM
15. ### calculate p value significance

How to calculate p value significance for the following? We educated 334 individuals over the age of 50 about cancer. 87 (26.05%) of them made...

• Replies: 2
• Views: 203
08-27-2016, 06:48 AM
16. ### Help on Bhapkar's Test using SAS/R/SPSS?

Hi All, I am currently wandering in the unfamiliar territory of the Bhapkar's test, and hopefully someone can provide some guidance... Please see...

• Replies: 3
• Views: 320
08-22-2016, 09:47 PM
17. ### Help with statistical power?

Hi, I'm doing a study looking at the ability of a test to detect a change in bacterial numbers pre- versus post-treatment . I've done a chi-square...

• Replies: 2
• Views: 174
08-21-2016, 03:01 AM
18. ### Graphpad or SPSS way to analyze this question

Dear friends, I have ~3500 patients. I have ages for everyone of them, and i have a laboratory value for each one as well. I want to know if the...

• Replies: 4
• Views: 225
08-15-2016, 08:48 PM
19. ### Fisher Test for 5x2 table with SAS or R

Hi, I wish to perform a Fisher Test for a 5x2 contingency table. I have a patient population divided in to 5 treatment groups, each with a...

• Replies: 3
• Views: 184
08-13-2016, 11:38 PM
20. ### How to obtain an unbiased post-stratified estimator for survival probabilities?

Suppose I have estimated the survival probabilities $\hat{S(t)}_1, \hat{S(t)}_2, \ldots, \hat{S(t)}_H$ from $H$ strata. Now I want to get an unbiased...

• Replies: 1
• Views: 180
08-13-2016, 09:24 AM
21. ### Repeated Measures Analysis with a long baseline period

I am currently attempting to analyze the efficacy of a treatment on a premature baby's SpO2 levels. I have many measurements before the treatment...

• Replies: 0
• Views: 181
08-08-2016, 10:41 AM
22. ### Mean and SD of two means and SD

If we have two groups of males, group 1: age >60 and group 2 <60. each of these groups have mean and SD; can we calculate a mean and SD for all...

• Replies: 13
• Views: 509
08-04-2016, 11:36 PM
23. ### Beginner questions: Clinical trial

Hi there! I am a medical student working on my PhD, and I am analyzing some data for a meeting. Since we don't learn much about statistics (at...

• Replies: 0
• Views: 163
08-03-2016, 02:37 PM
24. ### Interpreting odds ratio in ordinal logistic regression

Hi All, My data is from an educational programme for students. Questionnaire data was collected pre-intervention and post-intervention. We are...

• Replies: 2
• Views: 227
08-03-2016, 01:31 AM
25. ### Is this the right away to perform a trend analysis in a r*c table?

I might be not posting the question in the right forum since I didn't get any advice so far (after 20 viewers) and my project is a public health one,...

• Replies: 1
• Views: 197
08-01-2016, 01:01 PM
26. ### Intrarater reliability for continuous variable

I was hopeful for some advice on how to assess intrarater (not inter) reliability. My specific problem is 1 rater repeats a measurement on 20...

• Replies: 2
• Views: 223
07-30-2016, 12:22 PM
27. ### SAS Coding to find averages for every 60 observations

Hi. I am working on an analysis for research on premature baby health. I ran into a SAS coding issue which I hope some of you can help me with. ...

• Replies: 10
• Views: 312
07-29-2016, 01:38 PM
28. ### Paired or Unpaired T-test?

If I have traps set to capture a certain animal at night vs. during the day, would I use a paired or unpaired T-test? I'd be comparing the mean...

• Replies: 3
• Views: 337
07-28-2016, 03:22 PM
29. ### Cox's regression

Hello, I have some experimental data for animals with tumours. Unfortunately, they were not followed individually during a time course, but...

• Replies: 0
• Views: 259
07-27-2016, 06:03 AM
30. ### starting in biostats and need to analyse clinical data. how to begin.

Hello everybody I am a very beginer in stats and in using SPSS. I need to analyse some clinical data. I want to know please if this is a good...

• Replies: 1
• Views: 310
07-22-2016, 03:54 PM
31. ### Which statistical approach?

Dear all, I am a biologist with a very poor statistical knowledge so please excuse me if my question is not very well formulated- I am doing my best...

• Replies: 4
• Views: 389
07-18-2016, 09:41 AM
32. ### Correct analysis of crossover trials

Hi everybody I was wondering if anyone here had any expertise regarding analysis of crossover trials. I'm writing my thesis at the moment and...

• Replies: 1
• Views: 170
07-18-2016, 08:29 AM
33. ### Author's interpretation of Odds Ratio and Confidence intervals

Hi all, Having some difficulty understanding the results of this paper I am including in a review. It compares the effects of 3 interventions...

• Replies: 1
• Views: 191
07-16-2016, 08:16 AM
34. ### What does a mean probability mean?

Hi all. If each case in a dataset is assigned a probability of a certain event having occurred (based on their own individual data) and I...

• Replies: 1
• Views: 237
07-13-2016, 07:05 PM
35. ### Computing age and gender standardised mean BMI

Hi, I'll appreciate a lot if someone could tell me how to compute age and gender standardised mean BMI in stata. Thanks. ZZ

• Replies: 0
• Views: 328
07-10-2016, 08:20 PM

I'm trying to help my wife with some statistics. She's looking to see if people with Removable Dentures (RD) have a higher prevalence of Combination...

• Replies: 1
• Views: 262
07-09-2016, 03:35 AM
37. ### power calculation for two groups (parallel)

Hi I have got 400 and 600 samples in control and test groups respectively. And in each of these two groups, i have an effect variable that occurs at...

• Replies: 2
• Views: 214
07-08-2016, 10:54 AM
38. ### SPSS, descriptive statistics, crosstabs, risk

the problem has been solved. thanks

• Replies: 0
• Views: 196
07-07-2016, 03:36 AM
39. ### Parallel Bioequivalence Study Sample Size

I need to calculate the required sample size given the following information: Power=80% Coefficient of variation for Cmax and AUC = 40% True...

• Replies: 0
• Views: 279
07-04-2016, 03:26 AM
40. ### How to prove two methods are “similar”?

We are testing two imaging machines. One of the machines has been validated numerous times. However, we built the new machine and we need to prove...

• Replies: 1
• Views: 328
07-01-2016, 10:40 AM
41. ### External Validation of Cox Model

I have two data set (training and validation) for building and validating a Cox model. With the training data set I fitted a cox model using...

• Replies: 8
• Views: 507
06-29-2016, 04:18 AM
42. ### Help interpreting an interaction in Binary Logistic Regression

Firstly, thank you for taking the time to read my problem that I am having. The goal: interpret the direction of the interaction term. ...

• Replies: 3
• Views: 346
06-25-2016, 04:05 PM
43. ### Calculating standard deviation from mean and P value

I am doing a systematic review and one of the papers I am including has reported the data only as mean, sample size and P value. I need the mean and...

• Replies: 10
• Views: 575
CMP
06-24-2016, 10:10 AM
44. ### Permutation correlation with one non-normal variable

Hi, I am trying to assess the relationship between a relatively normally distributed variable (brain volume) and a strongly right-skewed...

• Replies: 1
• Views: 236
06-24-2016, 02:45 AM
45. ### Computing effect size with adverse event counts?

Hello! I'm working on a meta-analysis, and I have a special problem regarding effect size. Can anyone lend me some insight? I have a treatment...

• Replies: 1
• Views: 440
CMP
06-22-2016, 05:34 PM
46. ### Triple crossover study and multivariate model with paired data

Hi, I would like to analyze data from a triple crossover study. Same population received same drug (or placebo) three times a day with...

• Replies: 1
• Views: 390
06-21-2016, 06:50 AM
47. ### Statistical Approach for data (uneven intervals)

Hello, What statistical approach would you recommend for a data of the following pattern. In a 12-hour window, each row/ID is an independent...

• Replies: 0
• Views: 241
rvr
06-20-2016, 12:23 PM
48. ### Test for ordinal DV in mixed design

What's the corresponding test to Two way Mixed ANOVA when the DV is ordinal? I have two treatment groups, 14 time points and the DV is an ordinal...

• Replies: 0
• Views: 565
06-14-2016, 06:55 PM
49. ### Repeatability and Logistic Regression?

Hi all, my stats knowledge is quite basic so I would appreciate any help you can provide! I am working on a study looking at inter-grader and...

• Replies: 2
• Views: 351
06-10-2016, 02:02 PM
50. ### Is this study a case-control or retrospective cohort?

"Recently we retrospectively examined the spine on pyelograms of 34 children with Wilms tumour. The findings were compared with those obtained in 148...

• Replies: 0
• Views: 309
06-02-2016, 11:44 PM
51. ### Significance of a Dichotomous Variable Over a Continuous Variable

Hi all! I ran an analysis using the 2005 healthy eating index (HEI) score as the dependent variable and am a bit confused by my results. The HEI...

• Replies: 1
• Views: 298
06-01-2016, 06:24 AM
52. ### Chi Square for Molecular Screening Comparison

Hi, I'm trying to run a chi square test to compare two different screening methods for a pathogen. I'm testing this by diluting a known positive...

• Replies: 0
• Views: 183
05-31-2016, 03:59 PM
53. ### Best Statistical test for data

Hi All, Just wondering if someone could help with an issue with my data. I am wanting to analyse the relationship between continuous variable...

• Replies: 3
• Views: 418
05-26-2016, 06:49 AM
54. ### ANCOVA assmptions not met.

Hi, What is the non parametric alternative for parametric ANCOVA if we find that some ANCOVA assumptions are not met? How it can be done in SAS?

• Replies: 1
• Views: 217
05-25-2016, 04:03 AM

Hi, I was wondering if you guys can provide some ideas on best test for my samples size, since I am not very stat savvy. My project consist of...

• Replies: 4
• Views: 362
05-24-2016, 09:03 AM
56. ### Frequency analysis

Hello. I have a problem with my analysis. I got 2 groups which take drug (Group 1 (50 people) takes real medicine and Group 2 (40 people) takes...

• Replies: 7
• Views: 492
05-23-2016, 08:12 AM
57. ### Non parametric multivariate analysis. maybe :(

Hello to everyone, i need some help with my statistical analysis. I have two different pharmacokinetic parameters. They result from two different...

• Replies: 4
• Views: 435
05-20-2016, 04:07 AM

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