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

learn more… | top users | synonyms

1
vote
0answers
43 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
14 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 ...
1
vote
1answer
30 views

How to calculate degrees of freedom for chi squared test

I am very new to stats, and if the chi squared test is not the best way to handle this, please let me know. To simplify what I'm trying to do, I have many separate lists of genes. Each list is a ...
0
votes
0answers
17 views

How do I calculate the p-value in a gene enrichment analysis, using parametric and non-parametric methods?

I have a list of 20 QTL from an experiment involving a certain phenotype related to bone development. Of all the candidate genes within the 20 QTL intervals, 5 are associated with a certain disease ...
2
votes
1answer
43 views

statistical analysis of events in a given time interval

I am attempting to analyze biological data, to see whether the number of events in a given time interval is more/less than expected based on the overall frequency. How would one approach this? An ...
1
vote
1answer
200 views

Correlations between continuous and categorical (nominal) variables

I would like to find the correlation between a continuous (dependent variable) and a categorical (nominal: gender, independent variable) variable. Continuous data is not normally distributed. Before, ...
1
vote
0answers
33 views

How to perform statistical test for enrichment of gene lists?

In a typical ChIP-Seq experiment, we found a transcription factor ABC peaks on 590 genes. 242 genes out of the 590 genes are classified as ...
1
vote
0answers
12 views

Prioritization based on three factors

Background: Sales reps visit doctor and detail about a product/drug. One visit is termed as one call. In return he writes the prescriptions to doctors prescribing that particular drug. Problem ...
0
votes
0answers
27 views

Which statistics to use?

I have a medical research in which I have two sets of data Control group: People who have no ailment. Study group: People who have some particular ailment. Within each category there are ...
2
votes
0answers
37 views

Poisson regression in R glm(): concept and practice

I have a dataset data about a group of persons developing events with Poisson distribution. These events are uniform and can be recurrent in some of the subjects. ...
1
vote
1answer
33 views

Calculating variance for microarray data?

I have microarray data in which there are three biological replicates for each of the conditions. I am interested in a numerical estimate of how well the replicates correspond with one another, so I ...
0
votes
0answers
85 views

Inferring the statistical tests performed in a paper

I am in great need of help in order to infer the statistical hypothesis tests performed in Xanthelasmata, arcus corneae, and ischaemic vascular disease and death in general population: prospective ...
1
vote
0answers
10 views

Statistical technique to assess nutrition

My goal is to find risk factors for a disease. I think that a malnutrition is a risk factor for this disease. I have 5 variables that indicate the frequencies of ...
2
votes
1answer
35 views

Statistical paired test for relative change

Do you have any suggestions, which test I should use in order check if the relative change is statistically different than 0. I am sure that I should check the relative (fold) changes. Specifically, ...
0
votes
1answer
30 views

What is a tertile average of a group?

I came across a paper , where they have taken tertile average of a hormone level in a group. I am wondering what difference does calculating tertile average make? Thank You!
1
vote
1answer
45 views

Needing help in order to infer the statistical hypothesis tests performed in an old paper

I am in great need of help in order to infer the statistical hypothesis tests performed in an old paper. However I need to make some reasonable guesses only from the abstract of the paper since the ...
0
votes
0answers
30 views

What are the data needed to conduct Cost-Effectiveness Analysis?

I'm aiming to conduct a cost-effectiveness analysis (CEA) of the introduction of a new vaccine for HPV (Human Papillomavirus), in a developing country ( I think this will be done from the societal ...
1
vote
1answer
55 views

Quantifying applicability domain for predictive models?

I have a big dataset and I want to build a classification model (svm, rf, ann etc.). Then I split the original dataset into training set and test set. I build the model using training set. After it ...
1
vote
1answer
29 views

Programs and procedure for Blackwood test?

I am looking for programs and procedure for the Bradley-Blackwood test, which is normally used to assess test-retest reproducibility.
0
votes
0answers
30 views

Training models for classification using different negative datasets

I'm working on a massively unbalanced binary classification task - Classification of given protein sequences as belonging to a certain (very small) class, or not. There are about 1,300 positive ...
0
votes
1answer
45 views

Any known example of research project being led by statistician in public health

(I am fully aware that my topic may not be relevant here, do let me know if this is true.) I am a research staff with training in epidemiology and biostatistics, working in government organization on ...
0
votes
0answers
36 views

Good reference book for statistics in medicine

I am looking for a good reference book for applying statistics to medical problems. I am interested in a practical book that describes concepts including statistical power, tests for comparing ...
0
votes
1answer
53 views

A Conditional Probability Problem

This is a biological problem, however the problem requires a statistical solution, so therefore I'll keep it as abstract as possible in order for statisticians to be also able to contemplate it - I'm ...
0
votes
1answer
40 views

which statistical test to use to compare 3 different types of regions? [duplicate]

I want to compare the percentage of a species in 3 different types of regions. Which statistical test should I use??
1
vote
0answers
34 views

Testing for significant difference in mortality rate between multiple groups

How do I test for a significant difference between the mortality rate of 4 groups (each group with a different n) group 1: mortality rate = 30.9%, n=55 group 2: mr = 0%, n = 4 group 3: mr = 23.3%, n ...
1
vote
1answer
23 views

Creating a translated sample by subtracting mode

Consider a sample $x_1,...,x_n$ which we will call the original sample. To create a translated sample $x_1+c,...,x_n+c$, we add a constant $c$ to each sample point. Let $y_i=x_i+c, ...
0
votes
0answers
31 views

Project in Bayesian biometrics

I'm working on a project about specific bird species on an island in the Northern Atlantic sea. The data seem reliable and pretty detailed, and range from the 18th century, however their structure and ...
0
votes
0answers
28 views

what kind of statistic test should I use for my data?

I am working with biological data. The project is about comparing microbiota composition in different samples who have different type of diet. Here is the experimental design of the project: ...
2
votes
0answers
43 views

What is the null hypothesis in the definition of Sensitivity and Specificity?

I have hard time to understand that what is the null hypothesis in the definition of Sensitivity and Specificity here? I'm student of Statistics and from my little knowledge in this field I can see ...
0
votes
0answers
29 views

design and analysis of experiments

Kindly recommend some teaching material for "design and analysis of experiments" for the students of biostatistics and epidemiolody. Pls note that the students have only little knowledge on ...
0
votes
0answers
17 views

How to summarize mean +/- S.D. across disease severity

I am performing a meta-analysis and I have several papers that measure compound X in the blood of patients with a given disease. These papers have classified patients into groups based on disease ...
0
votes
0answers
24 views

Relation between median follow-up and median survival?

When follow-up is assumed to be constant and variable, is there any relationship between median follow-up and median survival? I.e. should one be less or greater than the other?
0
votes
0answers
79 views

Cumulative standard deviation calculation

I have a calculated daily survival probability, and associated SE. From this I can obtain the standard deviation. I have to report the cumulative survival over a specific period. So for example, for a ...
1
vote
0answers
23 views

Help in interpreting AUC values from ordinal variables

I would appreciate if someone could explain to me the benefit of using area under ROC for evaluating agreements between two raters. Here is an example from two raters on, let's say, clinical time ...
0
votes
0answers
34 views

Assumption with alternative hypothesis?

I am testing the reproducibility of two drug concentrations between two sites of the same individual. I am assuming response between sites should be similar. To test the significance I created a ...
1
vote
2answers
67 views

Can I use t-test to compare my control and sample mean to confirm significant difference?

My control is a sample without any drug treatment. My samples are treated with drugs. They were both randomly taken from a normal distribution. The hypothesis is $\text{H}_0: \mu = \mu_0$ and ...
2
votes
2answers
58 views

Prognostic factor vs. risk factor

As far i understand the difference between Risk factor and Prognostic factor is : Risk factor is the ...
3
votes
1answer
68 views

Hypothesis testing with very few data

My biologist friend is having a bad time with her experiment. It's suspected that changing the temperature and organic content in water may affect the growth of crustaceans. In her experiment, two ...
2
votes
0answers
49 views

Which statistical test to use and why?

My project involves 1) Comparison of new samples against a control and 2) Find any effect on the speed of growth and germination % of seeds by treating them with the new samples My question is, what ...
1
vote
1answer
95 views

Problem with identifying outliers

I'm running a biological experiment with rodents, have two groups (each consists of 26 animals), where one is treated with a chemical, and one is control (saline). In one variable, there doesn't seem ...
1
vote
0answers
51 views

Determining if experiment data can be pooled from multiple experiments

We have a dataset with Time and Treatment as independent variables, and growth volume as a dependent variable. The experiment was repeated on three occasions, with multiple time points and multiple ...
9
votes
2answers
219 views

The $z$-test vs the $\chi^2$-test for comparing the odds of catching a cold in 2 groups

I just read in a rather well-respected (popular) science magazine (the German PM, 02/2013, p.36) about an interesting experiment (without a source, unfortunately). It caught my attention because ...
0
votes
1answer
312 views

Making a cumulative incidence plot in R

Background I have a survival object in R called km. ...
0
votes
1answer
77 views

Defining a threshold for percentage data with high amounts of exact zeros

I am trying to analyse my biological data which is derived from flow cytometry and describes the percentage of cells with a certain property. Data is available for two conditions: once the cells ...
0
votes
0answers
36 views

Statistical Tests for comparing groups

I am a biologist and I have developed an algorithm that has the ability to identify and quantify fluorescent objects within the nucleus of a cell when imaged in a fixed state under a microscope. The ...
0
votes
0answers
24 views

Difference between t value and p value [duplicate]

I am not clear about how exactly the p values and t values are used. I know how to calculate them but I am not clear about the basic concept behind them. Any help ?
0
votes
0answers
43 views

review papers on P-values, adjusted P-values and common statistical tests in bioinformatics

I'm looking for review papers which give comprehensive reviews of P-values, adjusted P-values and common statistical tests in bioinformatics.
0
votes
0answers
39 views

How to estimate true concentration level of antibodies according to optical density in ELISA?

In ELISA Is it necessary to obtain true concentration level of antibodies for diagnosis? Is there a model allowing us to do so? I know there is a 4-parameters logistic model, but will people ...
0
votes
1answer
56 views

Count data with continuous variables

Let's assume one has looked at the occurence of a plant species at different altitude, different temperature and environment. Here are its data: ...
2
votes
1answer
97 views

Good introductory biology/genetics readings for statisticians?

I'm looking for books on genetics or biology in general, at an introductory level, ideally where topics are tackled from a statistical point of view. I've been reading "Genes population and languages" ...