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# Forum: Biostatistics

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

1. ### Question about sample size penalty for looking at data mid-trial

Hi, we're running a clinical trial for a skin treatment with a medical device that has a strong effect. We are using an inter-patient control (no...

• Replies: 0
• Views: 68
Yesterday, 04:58 PM
2. ### Help for sample size calculation

in my prospective cohort study I will assess the serum level of a vitamin in a group of patients the normal reference serum range is 10-30 in normal...

• Replies: 1
• Views: 124
10-23-2016, 11:37 AM
3. ### Correlated variables in Cox model - which one is best

Hi there, I am building a Cox model. I have two variables that are different measures of the same thing and they are therefore correlated with each...

• Replies: 0
• Views: 77
10-23-2016, 09:27 AM
4. ### HELP with data collection methods and data analysis in quantitative research : )

I am doing a research proposal on the effect of a drug on haemorrhage growth in traumatic brain injury. My null hypothesis: TXA does not reduce the...

• Replies: 1
• Views: 96
10-22-2016, 12:53 AM
5. ### Appropriate statistical test for HR's comparison between 2 population

In case of 2 population, the first has HR X for the study's outcome (between the exposed and non-exposed groups), and the second has HR of Y (between...

• Replies: 1
• Views: 114
10-21-2016, 06:02 AM
6. ### Which statistical test to use for my data analysis

Hi everyone, Could someone help me to know which statistics should i use for my data analysis. I did my project on "personal exposure...

• Replies: 4
• Views: 203
10-19-2016, 05:39 AM
7. ### Dataset for statistical analysis

Dear all, I work in Rome for the Italian National Health Service (www.iss.it); I am currently working on a European clinic project called EMTICS...

• Replies: 3
• Views: 166
10-18-2016, 10:26 AM
8. ### Recurrent Event Survival Analysis

Hi there, I'm working on a research on individuals who enter financial distress using the Cox proportional hazards model. In this case the...

• Replies: 0
• Views: 95
10-17-2016, 07:46 AM
9. ### Sample Size Calculation (HELP!)

Hi all, I wish someone could help me out. I am trying to estimate the sample size for a national health survey. From the previous report,...

• Replies: 1
• Views: 173
10-14-2016, 05:22 AM
10. ### Markov Process to estimate time until death

Are there any websites that show examples of data setup and SAS code using some sort of Markov model to estimate time until or probability of death?...

• Replies: 0
• Views: 177
10-05-2016, 12:14 PM
11. ### Which comparison of means test to use?

I've got myself confused about which test to use. I have done a cross sectional survey exploring the difference between pain as measured with a...

• Replies: 1
• Views: 192
10-04-2016, 11:14 AM
12. ### comparing sensitivity, specificity, and PPV of different cohorts-is it possible?

hello and thanks in advance for helping out! i hope that my questions will not be terribly on-profesional .. i'm trying to figure how to compare...

• Replies: 2
• Views: 112
10-03-2016, 11:24 PM
13. ### Poll: How do you handle subjects having very different patterns?

Good day everyone - I am curious as to what you all do in these situations. If you are running a sleep study, and you are simply using two...

• Replies: 2
• Views: 239
09-26-2016, 12:14 PM
14. ### 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: 328
09-16-2016, 02:29 PM
15. ### 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: 243
09-16-2016, 04:20 AM
16. ### 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: 205
09-14-2016, 02:54 PM
17. ### 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: 288
09-13-2016, 01:44 AM
18. ### 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: 137
09-12-2016, 03:21 AM
19. ### [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: 201
09-08-2016, 05:34 AM
20. ### 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: 223
09-06-2016, 11:14 AM
21. ### 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: 384
09-04-2016, 01:14 PM
22. ### 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: 197
09-02-2016, 03:46 AM
23. ### 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: 164
09-01-2016, 02:19 PM
24. ### 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: 403
08-30-2016, 04:01 PM
25. ### 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: 182
08-30-2016, 01:21 AM
26. ### 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: 178
08-29-2016, 01:42 PM
27. ### 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: 291
08-29-2016, 03:50 AM
28. ### 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: 262
08-27-2016, 06:48 AM
29. ### 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: 398
08-22-2016, 09:47 PM
30. ### 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: 218
08-21-2016, 03:01 AM
31. ### 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: 269
08-15-2016, 08:48 PM
32. ### 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: 246
08-13-2016, 11:38 PM
33. ### 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: 226
08-13-2016, 09:24 AM
34. ### 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: 225
08-08-2016, 10:41 AM
35. ### 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: 598
08-04-2016, 11:36 PM
36. ### 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: 213
08-03-2016, 02:37 PM
37. ### 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: 291
08-03-2016, 01:31 AM
38. ### 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: 263
08-01-2016, 01:01 PM
39. ### 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: 288
07-30-2016, 12:22 PM
40. ### 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: 385
07-29-2016, 01:38 PM
41. ### 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: 412
07-28-2016, 03:22 PM
42. ### 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: 349
07-27-2016, 06:03 AM
43. ### 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: 390
07-22-2016, 03:54 PM
44. ### 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: 448
07-18-2016, 09:41 AM
45. ### 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: 206
07-18-2016, 08:29 AM
46. ### 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: 241
07-16-2016, 08:16 AM
47. ### 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: 292
07-13-2016, 07:05 PM
48. ### 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: 371
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: 301
07-09-2016, 03:35 AM
50. ### 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: 262
07-08-2016, 10:54 AM
51. ### SPSS, descriptive statistics, crosstabs, risk

the problem has been solved. thanks

• Replies: 0
• Views: 230
07-07-2016, 03:36 AM
52. ### 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: 315
07-04-2016, 03:26 AM
53. ### 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: 411
07-01-2016, 10:40 AM
54. ### 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: 558
06-29-2016, 04:18 AM
55. ### 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: 401
06-25-2016, 04:05 PM
56. ### 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: 642
CMP
06-24-2016, 10:10 AM
57. ### 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: 270
06-24-2016, 02:45 AM
58. ### 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: 475
CMP
06-22-2016, 05:34 PM

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