The science of statistics applied to the analysis of biological or medical data.

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6
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1answer
290 views

What does a random walk do exactly?

To be honest, I have read many websites and answers regarding to this question, and none explained it in simple words which are understandable. What I want to do is to understand what a random walk ...
-1
votes
0answers
11 views

Negative Binomial [on hold]

I was fitting poisson count model in SAS and now proceeded with the negative binomial (NB). Can we change scale deviance in NB in SAS. I know we can change in Poisson model
2
votes
1answer
23 views

Probability of a deleterious mutation, given an observed distribution of mutations

This problem has been driving me crazy for days, so I finally resort to asking for help here: Consider a set of genes, where each gene consists of a sequence of letters, for example ...
0
votes
0answers
15 views

compute the ratio of odds ratios and its confidence interval

How would one compute the ratio of odds ratios and its confidence interval? for example: OR1=1.07; ci=0.88-1.29 OR2=1.27; ci=0.78-1.39
4
votes
2answers
161 views

Reconstruction of Species Distribution based on poorly-sampled data

cross-posted to Signal Processing, World Building, and Biology Stack Exchange Problem: After reading a series of fantasy novels, I noticed that the biosphere in that world made no sense. To clarify, ...
0
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0answers
8 views

Cronbach's alpha

I want to use the EAT-26 in my study , and the zero frequency is high in scoring because more than one answer represent zero in scoring ( never=0,rarely=0,sometimes=0) , so Cronbach's alpha is low ?! ...
0
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0answers
19 views

Kruskal-Wallis post hoc comparisons different results in different software used

I'm having some trouble analyzing my data because when I use StatSoft Statistica and run a Kruskal-Wallis, I get one set of values for multiple comparisons, but when the same analysis is run in XLSTAT ...
0
votes
2answers
70 views

Help performing hypothesis tests automatically on a large data set in R

I have a data frame in R with 100 variables (columns) and 100 observations (rows). Each row is a patient; the columns are different variables such as gender, height, body-mass index, etc. I know that ...
2
votes
1answer
84 views

How do you tell if you should use a one-tailed test or a two-tailed test in a t-test?

For example, how would you decide between which tailed test to do in the following experiment: Ethanol dilutions were made with different proportions and Daphnias were submerged in them to collect ...
0
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0answers
18 views

Statistical analysis of time to event data

If I have 2 events of interest, lets say $X$ and $Y$. I would like to know, what is the influence of $Y$ on $X$. It's like a correlation between 2 events, but I'm not sure what is the formal test for ...
0
votes
1answer
18 views

jackknifing blocks (*not* time series)

I have the following problem. There are 50 subjects. Each subject does a block of 100 trials. At the end I want to compute a complicated statistic s() on the data x. Now I want to be able to compute ...
2
votes
2answers
53 views

Biostatistics book for mathematician

It would be great if you could recommend me some books on biostatistics for people with a solid background in mathematics. I have an MSc in mathematics and a PhD in bioinformatics/machine learning, ...
1
vote
1answer
28 views

Are sensitivity and specificity complement of each other?

Sensitivity : probability that a person with the condition will be classified in one's study as having the condition. ...
0
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1answer
23 views

Why is screening test more concerned about sensitivity while diagnostic test is more concerned about specificity?

Screening Test : A large number of apparently healthy people are tested to identify those who are at a risk of the condition or disease. ...
7
votes
1answer
105 views

DNA exoneration: what are the chances?

As with any biometric, both the False Acceptance Rate (i.e. what is the chance that two samples of different individuals match) as well as the False Rejection Rate (i.e. what is the chance that two ...
0
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0answers
40 views

How can I use the posterior distribution of parameters from one model in another model?

I would like to model different effects of siRNA treatment on measurements. Cells are grown in 384-well plates, subjected to different siRNA treatment and then imaged to determine parameters. Around ...
1
vote
1answer
56 views

calculation of variance

Hi I have a question regarding calculation of variance of survey results. Consider the following example. If 5 (x) people answered a survey which consists of 3 (y) yes (1) or no (2) questions. You ...
1
vote
1answer
30 views

Controlled clinical trial, what is controlled refering to?

We say a (randomized) controlled clinical trial for a specific study design. Now my question is, what is controlled refering to? Different things come up to my mind: Controlled in the sense that ...
1
vote
0answers
36 views

How did they do this analysis? (weighted proportions)

I've read with interest the report by Ayanian et al "Racial and Ethnic Disparities among Enrollees in Medicare Advantage Plans" [1]. They have estimated adjusted proportions of individuals that ...
0
votes
1answer
51 views

What is a Dirichlet prior

I am doing some bioinformatics research but my background is Applied Math and I usually have trouble with the statistics part of it. Basically, I've created a Position Weight Matrix using a R ...
6
votes
1answer
160 views

What are hot research topics for PhD dissertation in Biostatistics?

I've been thinking of choosing research topics for PhD dissertation in Biostatistics. I wish to know some hot research topics in recent years. As far as I know, some hot research topics are: ...
1
vote
1answer
53 views

Find distribution of underlying feature

Let's say I have a dataset with values for the variable $W$. The distribution of $W$ doesn't follow any obvious known distribution. I have a model that gives $W$ as a functions of $E$ and $K, W = ...
1
vote
0answers
36 views

nested multilevel model for differential expression analysis

I have read several other postings regarding nested models, but they did not seem to exactly capture my particular case, and I'm a bit unsure how to proceed with analysis of my model. Any help would ...
1
vote
0answers
20 views

Can Anyone explain the significance of Q-mean value?

I have been using the Swiss Model for modelling protein structures. It returns the modelling result with the estimation of nativeness of the structure through the Q-mean4 value. I have even read the ...
0
votes
0answers
23 views

Separation of Two Sub-populations

Background: I have a large table with 7683 rows and 42 columns containing features of cells (endothelial cells), relating to their morphometric characteristics, for example the cell area, the longest ...
3
votes
1answer
70 views

Post-hoc after GLM: What does it exactly say?

Background: I have been asked to model the change of weight of a few animals undergoing experimentation via a simple GLM (General Linear Model). The data looks something like this. Note that all data ...
0
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0answers
36 views

Difference in Difference

How to interpret parameter of difference in difference with respect to public health ? Students had taken special care from 2010(baseline) to 2011(follow-up)period. say, in regression approach ...
0
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0answers
14 views

Modeling Switch-Like vs Continuous Signal

I'm currently trying to figure out the best way to model a given scenario, but am unsure of the best way to go about it, so I'll explain the situation in as much detail as possible. So I work in a ...
0
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0answers
14 views

selecting genes specific/agnostic to condition

I have a microarray transcriptomics experiment. The design of which is something like this : ...
0
votes
2answers
109 views

Machine Learning and Biostatistics [closed]

I am interested in a few areas with biostatistics, and was reading the course catalog at a university that offers machine learning. I am taking topology now, and i think machine learning uses ...
2
votes
1answer
161 views

Test(s) For Comparing qPCR results / ΔΔCт values

To be clear, I'm talking about real-time polmerase chain reaction (qPCR), not Principle Component Regression. Though from a company selling qPCR reagents, here is a good walk-through of the ...
0
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0answers
25 views

What books to read for Biostatistician position supporting product develpment for in -vitro diagnostics?

This is not a question concerning a specific statistical method, but I need an advice. I am interested in a position as a biostatistician to support product development for in-vitro diagnostics. I ...
0
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0answers
31 views

Testing of sensitivity for different algorithms

I have some queries I would like to discuss, I am doing some analysis for sensitivity. I am not from the field of statistics. I work with RNA-Seq data. The thing is I have found some genes which are ...
5
votes
1answer
36 views

Controlling random deviation in a birth-death process

I have a process in which $X$ is a molecule going through birth ($x \rightarrow x + 1$) and death $(x \rightarrow x - 1)$. Rate of both reactions, namely synthesis rate for birth and elimination rate ...
1
vote
1answer
96 views

Bayesian inference of a clinical trial for clinicians

I am a clinician who is more adept than average at interpreting clinical trials in a frequentist manner. At this point, interpreting a trial as a frequentist has kind of become a procedure: check ...
0
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0answers
14 views

Heterozygosity and the Wright-Fisher model

I was reading the textbook [Probability Models for DNA Sequence Evolution][1] by Durrett. In chapter 1, he discusses the Wright ...
2
votes
3answers
131 views

Beyond the basics: intermediate medical statistics textbooks suggestions

I am a soon-to-be physician. During my studies I have taken a class in biostatistics. I own Martin Bland's "An introduction to medical statistics", which was a required textbooks at the time, and ...
2
votes
1answer
35 views

wilcox.test usage in R

I would like to know if there is a difference in the values taken from measurements of a given characteristic sampled at primary forest (Point=1) and secondary ...
4
votes
1answer
119 views

Does an exponential model fit my data?

I am measuring accumulation of a fluorescent-tagged protein at a particular location within a cell over time. In previous experiments that I have performed, I see a standard exponential distribution ...
4
votes
1answer
98 views

Identifying the experimental unit

I have included a diagram of an experiment where cells are pooled from multiple animals, cells from the pool are then allocated to different treatments and a measurement is taken from each individual ...
2
votes
1answer
855 views

Standard Deviation After Subtracting One Mean From Another

I've got two sets of data from some fluorescent cells. The first set is when the cells don't have their fluorescence switched on, but they are still faintly glowing. The second set is when they do ...
0
votes
2answers
25 views

Interaction between variables

I would like to regress basal metabolic rate (BMR) on height, weight, age and gender. How do I do this taking into consideration the interaction between the variable? Wouldn't I have to consider ...
2
votes
2answers
96 views

Best distribution to handle a ratio of counts as a response variable

A quick statistics question (apologies for the added biology): I have two sets of counts (for the expression of two different isoforms of a particular gene), and to generate the response variable in ...
0
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0answers
26 views

Two way ANOVA or ANCOVA

I need to show that BMI of adults is neither age nor gender specific. Should I do ANCOVA or randomly make age groups and do two way ANOVA?
0
votes
0answers
35 views

Beyond multiple linear regression for longitudinal data?

I have a relatively large dataset from a longitudinal study (~100k subjects and ~10 random effects) where the outcome is a real-valued parameter. A simple run of R's ...
0
votes
0answers
24 views

minimum abundance of a bacterial species

I conducted a study in which I used sequencing of marker genes to study bacterial diversity and I would like to calculate the minimum abundance for a species to still be detected. The total volume ...
2
votes
1answer
70 views

How to measure the magnitude of difference between two gaussian distributions? Specifically with rates of DNA mutations

As the title says I want to quantify the difference in the rates of sequence change between genes. When I measure the mutation rates between my subgenomes I can determine a significant but slight ...
1
vote
1answer
184 views

Two-way MANOVA vs. two-way ANOVA on a composite variable

Is using a 2 way MANOVA to check whether height and weight differ across age groups and gender, the same as using a 2 way ANOVA to check whether BMI (wt in kg/ht in m$^2$) differ across age groups and ...
1
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0answers
70 views

Using repeated measures anova: Am I right?

We have just finished an experiment, where we had samples distributed into 6 groups and each group receiving a different treatment. Each group had 5 samples, with 20 replicate measurements taken per ...
1
vote
0answers
28 views

Type-1 Error of the Two-Stage Design

Background on Two-Stage Designs In clinical trials, we are often interested in the response rate $p$ for an experimental treatment. In a typical trial, we might expose $n$ patients to the treatment ...