The biostatistics tag has no wiki summary.
2
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1answer
31 views
Detecting variants of unknown significance
I have two groups of people, a healthy population which has carriers of disease and non-carriers, and I have a sick population. I know the frequency of genetic variants in both groups. I want to ...
0
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0answers
19 views
Which regions in two lines are more diverse?
I am novice in statistics and pardon me for my bad statistical terms. I have analyzed a data set for the presence of cis elements in promoter regions for some treatment genes. I have found the ...
0
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0answers
14 views
how to handle the test of significant of variances
Problem 1: Students' Profile
1.1 Age
1.2 Gender
Problem 4:
Are there significant variances in the technical competencies among the students in terms of:
4.1 unit assessment;
4.2 work attitude;
4.3 ...
-1
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2answers
183 views
Spearman's Correlation using Stata
I am trying to use Stata for the first time to calculate Spearman's Rank Correlation for differences in weight and hemoglobin between annual visits for a small dataset. Do I enter the differences with ...
0
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1answer
40 views
Removing the difference between treatments
Is there any statistical method to remove the difference between treatments observed before starting the treatments? I have measured the length of shoots on trees of three different treatments but ...
2
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0answers
30 views
Relationship between sample mean and sample survival probability
I am not sure if this question is very naive, but I was wondering if there is a relationship between sample mean and sample survival probability. For an exponential distribution with mean $\mu$,
...
0
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0answers
72 views
How to compare two survival percentages for two different populations?
I calculated the 5 year survival of two populations keeping different variable constant each time and got percentages.
I wanted to determine if these percentages were significantly different from each ...
0
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0answers
37 views
Choosing the most important variables in GLMs
I am struggling with this problem, can anyone tell me how can I choose the most important variables among several independent variables before fitting any models in GLMs? I really appreciate it. I ...
0
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0answers
57 views
Kullback-Leibler Divergence in laymans language
Can some one please explain me in lay mans term what is KL divergence method for divergence and what advantage it has.
Kindly help.
Thank you
0
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1answer
199 views
Determining if a set of experimental results is statistically significantly different from zero?
We have a dataset resulting from an experiment with a genotype A and a genotype B, which underwent either treatment X or no treatment Y, for four total sample groups. Each sample group had only three ...
1
vote
1answer
52 views
Dividing controls between two groups of cases
I have a set of data that contains cases and controls. I would like to divide the cases by a particular phenotype before running my tests, to see how these groups differ (but not necessarily to ...
2
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0answers
59 views
Using doctor's data to identify hospitalisations
I have access to two large medical datasets of observational records in the UK. The first - Clinical Practice Research Datalink (CPRD) - has data on 100,000's of patients - largely dates of doctor's ...
0
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1answer
37 views
Computing combinations
I am having a problem in getting all the combinations from my dataset. I need your suggestions and guidance in doing so.
I have a file, whose first column contains the regions and other file five ...
1
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1answer
81 views
Denoising of microarray data using PCA
I'm looking for references and comments regarding the validaty of the following method for data denoising, which I found while reading a code doing analysis of some gene expression dataset. The ...
0
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0answers
55 views
Is my Bayesian survival model correct and why does it take so much time to run?
I am a master student of biostatistics and am currently working on my thesis. I have written a semi-parametric accelerate failure time model for censored recurrent event data. The statistical ...
0
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0answers
138 views
Determining whether two samples come from the same population and which hypothesis test is appropriate
I have a study conducted by a team of doctors: two groups of people were treated for stress urinary incontinence in two ways: TVT and abbrevo. Each group consisted of 23 people. The hypothesis is as ...
0
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0answers
66 views
How to compute the confidence interval if I have 2 samples?
In the field of biology we often have >1 samples. For instance I can conduct two (but not many) experiments (replicates) each on a number of animals (n1, n2). The aim of the experiment is to estimate ...
1
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0answers
97 views
Sum of Squares reduction test: Convergence criteria met, but not all parameters of the model estimated
Background: I am using weighted non-linear regression to model the growth of plant organs, with dummy variables for different species. I am using a sum of squares reduction test (SSRT) to compare the ...
7
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3answers
139 views
Which kind of statistical exact test should I use?
I am testing a new kind of medicine against an older medicine in a very limited population. All the test subjects will first recieve the older, ineffective medicine. They will only recieve the new ...
2
votes
1answer
286 views
Difference between canonical correpondence analysis and canonical correlation analysis
I am no statistical geek and this might be a very naive question.....I am sorry before hand... please share your knowledge.
I am bit confused between two terms Canonical Correpondence Analysis and ...
5
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4answers
1k views
How does a Poisson distribution work when modeling continuous data and does it result in information loss?
A co-worker is analyzing some biological data for her dissertation with some nasty Heteroscedasticity (figure below). She's analyzing it with a mixed model but is still having trouble with the ...
2
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1answer
109 views
The biggest difference between medical statistics and biological statistics
I am turning my work from medical statistics into biology statistics (fishery). I am wondering if there is a big differences in methodology or focus between these two fields? In medical field, we do a ...
3
votes
1answer
181 views
Post-hoc analysis for Logrank test
I need to perform survival analysis for 4 different groups in a study. When I use the Logrank test, the null hypothesis is rejected.
My question is, how can I tell now exactly which pair of groups ...
3
votes
1answer
275 views
Three level mixed-effects (crossed and nested) model in stata
I am trying to fit a 3 level random and crossed effects model to a continuous outcome to estimate the respective variance components of each level of the 3 (for doctors)
Level 3: Physicians ID
...
1
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1answer
169 views
Concepts of mixed effects in statistics and econometrics, how to cope with them?
When I search for the definition about fixed-effects, random-effects or mixed-effects model here or elsewhere on the internet, there are a lot of discrepances. My first exposure to linear ...
2
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1answer
447 views
-1
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1answer
448 views
How to calculate sensitivity, specificity, and odds ratio?
I am trying to calculate sensitivity, specificity, and odds ratio of a data set, they are numerical values of percentages from 0% to 100%. How should I do the calculation?
Wikipedia has the formula:
...
5
votes
1answer
197 views
Is Ye Shiwen's 400m IM performance in Olympics “anomalous” statistically?
The 16-year-old Chinese swimmer Ye Shiwen swam more than 5 seconds faster than her personal best in women's 400m individual medley in London 2012 Olympics, winning her a gold. Her performance received ...
5
votes
2answers
841 views
What is the conventional definition of recurrence-free survival?
Hello to all the biostatisticians and epidemiologists out there,
I have looked up and down for a standard definition of recurrence-free survival, and the issue I'm having is determining if the ...
0
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0answers
302 views
How can I compare the effect of an pre-post intervention between two groups with multiple numeric dependent variables?
I have collected data from two groups (age 25-30, age 30+). In each group I have 10 patients. I performed several medical tests (i.e., R.B.C, Liver test, etc.) on the patients, before and after ...
3
votes
0answers
123 views
(Non-linear) Transformation of confidence interval for multinomial parameters
I have a certain computational biology problem I wish to model. Say I have a vector $\vec{f}$ that yields $\vec{p}$, of which the explicit form amounts to picking $\vec{p}$ as an eigenvector from an ...
0
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0answers
73 views
Concise book/tutorial for Statistics (Data Analysis) [duplicate]
Possible Duplicate:
What book would you recommend for non-statistician scientists?
Could anyone suggest a concise book/tutorial on statistics with examples. I am a biologist and need basic ...
1
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2answers
128 views
How to calculate similarity in gene expression for each gene in two conditions and rank them?
I have expression values (log2) for 200 genes in two conditions treated and untreated and for each condition I have 20 replicates.
The dataset looks like this:
...
3
votes
2answers
309 views
How to correct for inter-experimental variation in cell culture research?
I am testing cell cultures. I grow cells in a "control media" for 2 weeks. During these 2 weeks, the cells produce an antibody, and at the end of the 2 weeks, I measure the levels of the antibody. ...
1
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1answer
115 views
Estimating Diversity of operon types using HMMs across metagenomes: Mann-Whitney? Kruskal-Wallis? or other?
Question that seems complex but probably isn't.
I'm comparing 10 metagenomes (http://en.wikipedia.org/wiki/Metagenomics), that are supposedly unrelated (they are 10 geographically separate ...
0
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0answers
15 views
Predict values from the hglm2 package in R [duplicate]
Possible Duplicate:
Specifiy a complex random model in the HGLM package (R)
If anyone is the familiar with the HGLM package and the hglm2 function, I am trying to extract predictions from a ...
0
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0answers
102 views
Specifiy a complex random model in the HGLM package (R)
I'm using the R based HGLM package, and the hglm2 function to specify a model for which I have already written the code in Genstat.
The model spec in Genstat is as follow
...
8
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1answer
223 views
DNA use in court cases
I am currently studying the following case of Neil Owen, based on the following article I found a newspaper:
"A 20-year-old student was jailed for life yesterday for the brutal
rape and murder ...
0
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1answer
150 views
What statistical test should be used to accomplish the objectives of the experiment
I'd like to have your feedback to analyze my data from the following experiment.
Experiment Information
A total of 30 (15 from one city and other 15 from another city) slaughtered animals were ...
0
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0answers
196 views
Dixon test for outlier but which one is an outlier?
Following my previous question, I used Dixon test for outliers with the help of Michael Chernick answer. So now I have pvalues for say 10 numbers (basically 10 patients). But I have around 50k pvalues ...
2
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2answers
702 views
Cumulative Incidence vs. Kaplan Meier to estimate probability of failure
To estimate the probability failure in medical sciences, it is not atypical to use 1-KM. However this does not account for competing risks, such as death by natural causes or causes unrelated with the ...
2
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1answer
290 views
What does mean by “the cumulative frequency in the form of probits”?
What does mean by the "the cumulative frequency in the form of probits" (see diagram)? How to use this methodology when one has only the Ratio and group information. I wonder how to compute these ...
2
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0answers
130 views
P-value approximation from an underlying unknown distribution
I am calculating a certain statistic(relative entropy) of a certain sequence alignment over DNA sequences. The statistic has a certain distribution in the entire genome of which I only have 1000 ...
1
vote
1answer
468 views
How to find differentially expressed genes in R?
Can you tell me some procedures in R, which are able to find differentially expressed genes for a given microarray data?
Moreover,If you can give some ideas related to clustering of significant ...
1
vote
1answer
145 views
Statistical tests for low sample numbers in both indendent groups (n=3 and n=1)
I've been asked to analyze some data for an experiment that's already been done. 15 rats were raised in 5 groups of 3
No treatment
Saline treatment (control drug is delivered via saline)
Drug ...
2
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2answers
232 views
Proper contingency table analysis for old diabetes study
I was chasing down a citation about the incidence of postoperative wound infection in diabetic patients, and I found this 1998 abstract by Pomposelli with the following statement:
"In patients with ...
0
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1answer
169 views
Statistical analysis of change in protein concentration during a disease
Concentrations of 50 proteins were measured in 50 normal persons and 150 patients. I am just wondering what kind of analysis will be most appropriate to finding out which protein concentration is ...
4
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0answers
282 views
Propagation of uncertainty/standard deviations in biological experiments
I am trying to work out how to propagate standard deviations in a biological experiment, but I have some difficulties.
I have the following (semi)fictitious data originating from an image analysis ...
2
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3answers
298 views
Good source of information about AMOVA
I'm looking for a good source of information about Analysis of Molecular Variance (AMOVA), a kind of statistical analysis used in population genetics. Especially how are the $\phi$-statistics ...
5
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0answers
371 views
Sample size and cross-validation methods for Cox regression predictive models
I have a question I would like to pose to the community. I have recently been asked to provide statistical analysis for a tumor marker prognostic study. I have primarily used these two references to ...
