1
vote
1answer
37 views

Compare two samples

similar questions have been asked but have not managed to get a conclusion from them. I am comparing two sets of samples, where ratios have been obtained for several analytes per sample. So the values ...
1
vote
3answers
96 views

Sampling data to have specific mean and standard deviation

I have a data that I want to sample such the resultant distribution of values should have specified mean and standard deviation. I can think of rejection sampling to achieve this however that seems to ...
2
votes
1answer
67 views

Non parametric Wilcoxon Signed Rank test

I have the following data vector(in fact its 2392 data points long): ...
0
votes
0answers
37 views

R package fitdistrplus: function fitdist shows unusual error

I used the package R fitdistrplus in order to estimate parameters of different distribution function. In one case it shows a strange error message I can't interpret: ...
0
votes
0answers
11 views

R: Shapiro-Wilk test with relation of W and P-Value? [duplicate]

I'm currently learning about the Shapiro-Wilk test for normality and using R for conducting simple experiments. One thing which is confusing me is that I found some results would produce a high W ...
1
vote
1answer
31 views

Compare distributions with uneven and small sample sizes

I will be performing my analysis in R but any general mathematical-based answers will be appreciated. I realize similar questions have been asked before but I am new to statistics so please excuse my ...
0
votes
0answers
24 views

How to interpret log-likelihood outputs from MASS::fitdistr (R)

AIM: Fit the best distribution to columns in a dataset (30k records) so that I can to go on to produce test data that is in a similar distribution. WHAT I'VE DONE SO FAR: Using R, I have found and ...
1
vote
2answers
92 views

How to use the chi-squared test to determine if data follow the Poisson distribution

The figure below (Figure 1 from p. 646 of this paper) compares observed values against expected values under the Poisson distribution. It then runs a chi-squared test to see if the observed values ...
1
vote
0answers
38 views

Asymptotic Distribution of beta distribution parameter

I am trying to create a t-interval for the first shape parameter of a Beta distributed variable based on a random sample. $ f(x;\theta,\beta) = ...
2
votes
0answers
74 views

Testing for overdispersion in logistic regression

R in Action (Kabacoff, 2011) suggests the following routine to test for overdispersion in a logistic regression: Fit logistic regression using binomial distribution: ...
1
vote
2answers
42 views

Appropriate distribution for bounded data set

I am designing a points-scored test. There is a limit on the maximum amount of points possible, as well as on the fewest amount of points possible. I have had a test group take the test and graphed ...
4
votes
1answer
168 views

Which distribution fits data better?

I use fitdistr in R to select which distribution fits my data best. I tried cauchy, ...
0
votes
0answers
45 views

how do I “build” a distribution from a list of values and then calculate p-values?

I have a list of values (A) that I consider to be the null distribution which I want to use to test the significance of another set of values (B) and get p-value for each item in B. I read this post ...
1
vote
0answers
48 views

Network graph: hypothesis test that degree distribution is becoming more equitable

I'm playing around with network graphs and am wondering how to show that there is: a statistically significant difference in in-degree distribution between nodes for 2 time periods the in-degree ...
2
votes
0answers
55 views

Comparing estimators in Cauchy distribution

Given $n$ observations with a Cauchy distribution (location=t,scale=1), I would like to compare estimators such as the mean and median by simulating sample means and mean square errors. This is an ...
0
votes
1answer
65 views

Finding a suitable distribution for data in R? [duplicate]

I have a set of data with summary as below: The data are non-normal and transformations did not obtain normality. Given the data are continuous I have narrowed the range of distribution down to ...
1
vote
1answer
70 views

Sample from a custom continuous distribution in R

I have a probability density function in R and I want to draw a single sample from it. How do I do that? My current solution (and the one Google keeps giving me) is to evaluate the function for a ...
3
votes
1answer
75 views

What do you do after testing if two non-normal distributions differ?

This is a follow up question to "How do I test if two non-normal distributions differ? I have 13 distributions, . According to the previous question, I should do the following. Kruskal-Wallis test ...
0
votes
0answers
15 views

Multivariate skew normal [duplicate]

In the maximum likelihood estimation of Skew Normal, how does R calculate the mean? You know the formula is \begin{equation} \mu=\frac{ \sum_{i} x_{i} W(x_{i})}{\sum_{i} W(x_{i})} \end{equation}. ...
5
votes
3answers
301 views

How do I test if two (non-normal) distributions differ?

I have read about Student's t-test but it appears to work when we can assume that the original distributions are normally distributed. In my case, they are definitely not. Also, if I have 13 ...
6
votes
2answers
282 views

How to compare measurements and uncertainties made with different measuring instruments?

I have two different measuring instruments, A and B, both measure the same physical property $x$ of an object but with different "quality": B gives measurements with a known uncertainty while I do not ...
0
votes
0answers
47 views

Distribution of Data

I have a question about glm model fitting of my data. The distribution shape is likely to follow a poisson distribution, but the response variable is not count/rate, but continuous decimals with ...
5
votes
1answer
166 views

How to describe/explain the shape of a distribution which has two peaks?

How can I describe the shape of the following distribution, which has two peaks? What are the important things in describing the distribution shape? It is the output of the following ...
1
vote
1answer
71 views

Analysis method for count data with unequal sample sizes and categorical predictors?

I have a problem I've been going over and over for months to find the right statistical analysis method. I'm planning to execute the analysis in R, so any mention of appropriate packages is also ...
0
votes
0answers
30 views

Bootstrapping for standard scores

I would like to compare data among different sets where the values span the same range (0,1] but will have different means and unknown distributions. Given the unknown distributions, I thought of ...
1
vote
0answers
94 views

Quasi Maximum Likelihood estimator for GARCH with jump (Compoud poisson process with normal distribution)

I have to modify some R code to take jumps into account in my modelisation. First I build a simulation of a Garch 1,1: $r_t=\mu+\sqrt{h_t}\epsilon_t$ $h_t=w_0 +\alpha(r_{t-1}-\mu)^2+\beta h_{t-1} $ ...
4
votes
0answers
63 views

finding position by regression fit

I try to estimate an underfloor pipe position based on a temperature distribution on a surface of the floor. I know there is the pipe emitting a hot temperature all way along. I can measure a ...
2
votes
0answers
157 views

Evaluating goodness of fit for distributions (e.g. LogNorm, Gamma, …) with estimated parameters using KS tests (and R)

Currently I am trying to find a well-known distribution that fits to my positive skewed dataset (n=70) the best. First I used the fitdistrplus R package to estimate ...
1
vote
0answers
32 views

Comparing two samples in mixtools

I have 16 experiments performed under different conditions and I would like to compare them between each other. Each experiment has 5-6 samples (cells). Each cell produces hundreds of data points each ...
0
votes
1answer
77 views

Generating correlated distributions with a certain mean and standard deviation?

Given a distribution A with a mean of $\mu_1$ and standard deviation of $\sigma_1$, how can I generate: Distribution B with a mean of $\mu_2$ and standard deviation of $\sigma_2$ and a correlation ...
4
votes
0answers
44 views

How do I model the probability of two empirical distributions?

I have two distributions: A, and B. Each distribution is filled with the numbers 1.0-10.0. These distributions are NOT simple functions, like the gaussian, but are merely empirical counts. ...
3
votes
1answer
81 views

Notation for Random Bernoulli-Like Vector With Fixed Sum

I draw a random vector of dimensionality $k$, each dichotomous element of which taking on a value in $\{0,1\}$. The probability that any element will be $1$ is captured in the $k$-dimensional ...
0
votes
1answer
79 views

Conflicting Normality Tests

I have been trying to establish whether I could model my data, a set of 90 observations, using the normal distribution. I have tried the Shapiro-Wilk and the Anderson-Darling tests but each came back ...
2
votes
1answer
116 views

Why am I not able to fit a zero inflated poisson distribution?

Following what is suggested here http://stackoverflow.com/questions/7157158/fitting-a-zero-inflated-poisson-distribution-in-r ...
4
votes
1answer
94 views

Probability Interval for Gamma Distribution

There is something that I am doing wrong in the exercise below and I would appreciate some help figuring it out. Let $X_1, X_2, \ldots, X_5$ be a random sample from a $\Gamma \left(3,3 \right)$ ...
4
votes
0answers
90 views

What analyses do I need to run?

Long post. Question at the bottom. My data look likes this: It consists of the test set accuracies of a series of 50 models formed on training sets. Using random sampling of the raw ...
0
votes
2answers
63 views

What is the relationship between the normal and the t-distribution in R (pt and pnorm)?

In R, is it true that: pt(q,df=Inf) $=$ pnorm(q)? Or in words, can I supply df=Inf in ...
2
votes
0answers
48 views

Noncentrality parameter in two-sample-t-test (Power analysis)

I am working with R, doing a post-hoc power analysis. Can anyone explain to me why these two commands generate different outputs? I thought they should not! ...
0
votes
0answers
32 views

Is it possible to construct an empirical “distribution” from empirical data?

I am trying to compare two (univariate) data sets using the HellingerDist function described here. However, this package only allows the a ...
3
votes
1answer
329 views

How to know if my data fits Pareto distribution?

I have a sample which is a vector with 220 numbers. Here is a link to a histogram of my data.. And I wish to check if my data fits a Pareto distribution, but I don't want to see QQ plots with that ...
4
votes
3answers
924 views

How to check if my data fits log normal distribution?

I'd like to check in R if my data fits log-normal or Pareto distributions. How could I do that? Perhaps ks.test could help me do that, but how could I get the alpha and k parameters for Pareto ...
5
votes
3answers
2k views

How do I check if my data fits an exponential distribution?

How could I check if my data e.g. salary is from a continuous exponential distribution in R? Here is histogram of my sample: . Any help will be greatly appreciated!
0
votes
0answers
26 views

Regarding negative binomial distribution in R

If a random variable follows negative binomial distribution with parameters $r$ and $u$ and $p=1/ (1+u)$, then how to draw a random sample from negative binomial using binomial distribution in R?
2
votes
0answers
178 views

Generate data from a t-distribution with specified mean and standard deviation

How does one randomly sample from a T-distribution in R. From what I've found, the function rt in R doesn't let you specify the mean and standard deviation. For a ...
5
votes
1answer
241 views

Generating survival times for a piecewise constant hazard model with two change points

When there are two change points in a piecewise constant hazard model then the density function becomes some triangle exponential distribution. In this situation I can't generate the survival time ...
0
votes
0answers
61 views

How to ´check if two (ergodic) distributions statistically differ (in R)

I need to check if two ergodic distributions statistically differ. I know about the Kolmogorov - Smirnov test. However, being the ergodics computed as in Feyrer (2003), Convergence by parts, I do not ...
2
votes
0answers
93 views

Estimating of point in the density of bimodal distribution

I'm trying to estimate a specific point in a bimodal distributions, It's the point that I indicated in my picture with the A. As example we can generate a mixture of guassian and then try to ...
0
votes
0answers
246 views

Generate random variables from the Gumbel distribution in R

I want to generate 1000 random numbers with Gumbel distribution (extreme value distribution type 1) with known parameters $m$ and $a$. Then I want to estimate the parameters of the distribution for ...
0
votes
1answer
424 views

Fitting a Poisson distribution with lme4 and nlme [closed]

I am now looking for a GLMM, which could fitted a Poisson distribution with a log-link. From what I see until now, lme4 allow to specify the family and the link function for ...
1
vote
0answers
101 views

Test if multidimensional distributions are the same

Lets say I have two or more sample populations of n-dimensional continuous-valued vectors. Is there a nonparametric way to test if these samples are from the same distribution? If so, is there a ...