Creating samples from a well-specified population using a probabilistic method and/or producing random numbers from a specified distribution.
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1answer
56 views
Sampling from the conditional distribution assuming sampling from the joint
I am struggling with this question, which I thought it should be easy: suppose we have a method of sampling from the joint distribution of a collection of (discrete ordinal) random variables. We do ...
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1answer
37 views
Sampling method for constructing multiple groups from a given pool
There is a set A having $N$ elements. Based on set A, I would like to construct $M$ groups, where each group has $P$ elements. Naturally, $M P <N$. All of those elements in the $M$ groups are ...
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1answer
181 views
How does confidence interval vary with sample size?
I am trying to convert state-level poll results for 2012 U.S. presidential election into state-level probabilities of each candidate winning. To achieve that, I am using the logistic function, which ...
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1answer
61 views
Exercise in testing a difference of means
A random sample of 49 Kwakiutl native Americans reported that they went fishing an average of 68 days each year. Information from a non-native local population showed that they fished an average of 66 ...
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1answer
150 views
Expected value of min X for bernoulli success?
I take a SRS sample of size n from a population of x values ranging from 1 to N. Each selected unit also has a probability p of success or q = 1-p of failure (i.e. the probability of success/failure ...
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1answer
111 views
Sample size determination for estimating proportion
We have a population of unknown size. Each element has a class A or B. We are trying to estimate the proportion of A's in the population. We can randomly sample from the population and for each ...
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1answer
52 views
How does sampling scheme affect some statistics of interest?
I have a sample of data sets A = {a1, a2, a3, ...aN}
We will change each data value following the same pattern, say a1’ =a1*10, a2’ = a2*10.
Which statistics evaluated from this data set will be ...
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1answer
150 views
Sampling to get around randomForest's 32 factor level limit
I'm trying to work around the randomForest package limit of 32 levels for factors.
I have a data set with 100 factors in one of the variables.
I wrote the following code to see what things would ...
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1answer
89 views
Design effects (or variances) of sampling methods?
Where I can find comparison of variances (or design effect) of different sampling methods?
Same population, same sample size: I want to know which one has smaller variance than other; in simple ...
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2answers
109 views
Combining expert estimates
I am trying to work on a process to improve how how well my team estimates. I want to look at using some statistics to help out and embrace the uncertainty in how we estimate tasks.
If I have a group ...
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1answer
70 views
Sampling plan for a large data set showing a given pattern
I have a large set of data sets. For instance, it has 30000 data points, which are identified as $1, 2, 3,\dots, 30000$. For notational purposes, $D(i)$ represents the data value for a point ...
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2answers
32 views
Finding the distribution when the observations are dependent
How do we find information about the distribution of a variable in presence of dependency among our observations? This dependency is coming from measuring the variable on the same group of subjects ...
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1answer
22 views
Sampling from a database
I am conducting a research study about breastfeedding. I receive a whole database of subjects which are suitable to my research. I have had to call each individual to ask for their approval to ...
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0answers
20 views
How to add confidence intervals to describe the variability in monthly samples of data?
The data analyzed here is a sample of individuals collected on a monthly basis. What would be the best way to compute confidence intervals for the monthly sample means, in order to indicate the ...
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0answers
16 views
Getting the degree of overlap between each pair of classes
In a dataset containing many classes, is there any way to get some values which indicate how much the data-points of two different classes $y_i$ and $y_j$ are overlapped ?
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0answers
22 views
Random Sampling [closed]
A college statistics class has 14 women and 11 men. If the professor selects a random sample of n= 4 students, what is the probability that 2 men and 2 women will be selected? What is the probability ...
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1answer
14 views
Weighted sampling from objects with costs
I have a set of models which I have fit using nonlinear regression to some data, and hence for each has an associated squared error, or cost. I want to sample an models in a manner which favours ...
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0answers
33 views
R Quadratic programming and constrained optimization problem [closed]
I want find a vector p which lies in the positive null space of a matrix S and as well minimize the value of a least squares function with respect to p. Constraints are thus that p>0 and S*p=0
Here is ...
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0answers
22 views
Might be a bit basic, but I need some help (samples)
If I was interested in observing a variable during different and sometimes very specific periods of the day (like the varying shift pattern, for person X over time)…
Am I correct in my thinking below? ...
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1answer
55 views
Determining butterfly weight distribution
I'm a researcher studying a specific butterfly species. I've conducted an experiment where I measure the weight of this species at different locations on the earth. The data is cateogorical and ...
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0answers
13 views
Discrete Fourier Transform and uneven sampling
In this blog article
an example is given of one can use the DFT to detect frequencies much higher than the sample rate.
In the comments sections I asked how it was done, since DFT normally requires ...
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0answers
12 views
How would you approach weighting of open response lists in a statistical manner?
How would you deal with lists of varying lengths? For example, if you asked for an ordered list of your favourite movies without any constraints how would you value the weight of someone who submits ...
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0answers
28 views
Sample changing distribution
I have the following process:
I have N buckets in front of me, $M$ of which are filled with water (the other ones are empty).
I pick one of them (consider uniform distribution) and empty it (so ...
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0answers
81 views
Why does the mean of the bootstrapped distribution not equal the original summary stat?
I have n samples and their average. There's some correlation so I used a moving block bootstrap to get an empirical distribution of the mean. The mean of this empirical bootstrapped distribution seems ...
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0answers
32 views
Can I improve data accuracy by taking many smaller samples? [closed]
Please excuse my lack of stats knowledge - it's been a while since I took Stats101.
Currently at my workplace we take a single 250g sample from a bin of product to analyse product quality. This ...
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0answers
15 views
Probability calculation for a ranked set sampling design
This question is an extension of my previous question that was very nicely answered by whuber. But now some new restrictions have been imposed and I am trying to figure out the form of the ...
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0answers
7 views
hypergeometric sampling [duplicate]
Hypergeometric Sampling involves lot=n, sample=s, defectives in lot=d, defectives found in sample=c. And the question is what is the Probability p of getting exactly 5 defectives from a lot of 50000 ...
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36 views
How to pick a sample from a multiple group, stratified population for repeat surveys
I provide support to about 500 internal customers on a computer system. I want to start measuring my 'customers' satisfaction on some kind of routine schedule. However my customer base can be ...
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0answers
36 views
Comment on this method of sampling from any distribution?
Say I have a distribution, either described by a probability density function that is integrable and continuous, or by a set of discrete probabilities over a finite set of symbols.
I want to ...
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0answers
19 views
Dealing with variance within a closed set
A naive question perhaps, but one I need an answer to.
I am developing the functional requirements of a machine that needs to accept and process a number of incoming items daily. Any model for ...
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0answers
213 views
2 samples, t test with multiple dependent variables SPSS
I am attempting to compare two samples in SPSS. I have taken a sample of 350 from group 1 and 350 from group 2. Now, I want to compare these two groups that are identified by a filter variable ...
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0answers
105 views
Bootstrapping Methodology
I have this bootstrap setting:
Given $n$ vector-valued statistics (each statistic is a vector) of dimension $r \times 1$, I generated $1000$ bootstrap samples and then generated an estimate of each ...
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votes
1answer
48 views
How can you find the probability that an element is part of a sampled set?
(I'm a bit of a newbie, so pardon me if I use incorrect terminology.)
Let's say I have a set of scalar values V that I sampled from a set S. I want to test whether a given value X could be a member ...
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0answers
44 views
Variable length word sampling problem
I have a unusual sampling problem.
I have a continuously growing file with millions of words in it. Each word can have 1 to 8 characters in them. A word can have duplicate characters in them. The ...
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0answers
32 views
Condition in conditioned latin hypercube sampling
I am trying to use conditioned latin hypercube sampling in R (clhs package, see here). Unfortunately, I don't really understand how the cost parameter can be used. ...
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0answers
73 views
Alternative sampling method instead of fractional factorial design
I am trying to do my design of experiment for numerical simulations. Here, i have (eg.) 10 parameters which can be 0 or 1 ...
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0answers
79 views
How can I tell whether my data is skewed due to sampling error?
I have some psychological data (N=100, 2 conditions) in which across 55 questions participants made an estimate, and then after a manipulation they made an additional estimate. I then calculated how ...
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0answers
96 views
Non-response bias
I have the following question:
In a survey, a simple random sample of 1,000 households was drawn to
determine the distribution of household size in a city. Interviewers
were required to visit ...
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0answers
54 views
What is the estimate of sample mean variance? [duplicate]
Possible Duplicate:
How does the standard error work?
What is the estimate of sample mean variance and how do you get it? Are my understandings of the following correct?
...
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0answers
111 views
Multi-stage sampling and sample representation
I have used mutli-stage sampling (i.e. cluster and stratified sampling) to select four units within a geographical area. Each unit was selected randomly from a list of that unit. There are only four ...
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0answers
24 views
sample vs population [closed]
A random sample of athletes completed an extraversion test. For a normal population the scale mean is 26 and the standard deviation is 6. The athlete sample extraversion scores were: ...
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0answers
47 views
Are there non-uniform random generator directly requiring random seeds?
I wonder if my following understandings about random seeds are correct:
Uniform random generators require random seeds.
Non-uniform random generators depend on random seeds, only through
uniform ...
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0answers
69 views
Using an Industry as the unit of analysis [closed]
The title of my PhD research is "The effect of Technology Transfer on competitive advantage in Omani oil and gas industry".
My research is a quantitative research and I'm going to use Structural ...
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0answers
41 views
Guidelines on assessing how data is gathered
I will be working with a dataset sample which I will use for optimization purposes. However, before I start, I want to briefly analyze data in order to get a better sense and identify possible ...
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1answer
33 views
Sampling subsegments from discrete input ranges
I have an set of input ranges {[a1, b1], [a2, b2], ...}. Each a and b represent integer ...
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0answers
23 views
Sample size determination for polling with multiple choice type questions [duplicate]
Possible Duplicate:
Question regarding sampling, estimation and accuray
Let's say there are N sets of diamonds, containing 5 in each set. There can be anywhere between 1 to 5 defective ...
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0answers
127 views
Comparing two methods of sampling from a bivariate normal distribution
Is it possible to have two different methods of sampling from a bivariate normal distribution with a non-identity correlation matrix in such a way that one method would "consistently" result in a ...
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0answers
82 views
Quantifying the error of an approximate probability distribution
I will approximate a given probability distribution $P$ over $\mathbb{R}^n$ with a distribution $\tilde{P}$ which is simpler to represent. I would like to keep track of the error that I'm making ...
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0answers
147 views
Sampling distribution [editted] [closed]
With a given mean , standart deviation, How can one determine the mean and the sampling distribution of the sample mean for a*random* sample of size n ( n is known and, of course it is an national ...
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0answers
134 views
Sample size needed to find all error values
This is a pretty basic question as I'm new to stats, but hopefully someone can help!
I have a sample size of 30,000 records and so far 6500 have been checked to see if an error exists - of these ...
