# Tagged Questions

Creating samples from a well-specified population using a probabilistic method and/or producing random numbers from a specified distribution.

339 views

### Philosophy of sampling for experiments: finite versus infinite

What is the difference between a finite population and an infinite one - when you are designing an experiment (sample/power and interpretation of the results)? Say a company has a database of 20,000 ...
120 views

### Cluster randomized sampling and subseqent analysis

I am currently designing the sampling strategy for a prevalence survey on elderly in long term care facilities (LTCF) in my service, I used the "Limebook" from WHO as a reference. And I would like to ...
57 views

### Calculating error in sampling

I have a certain population U. The members x of U each either satisfy or don't satisfy a property p. That is, p(x) is either true or false for each x in U. I want to get an estimate of the fraction ...
202 views

### Non-response rate

In a project that I am doing to evaluate customer behaviour, I have asked a set of questions such as whether they read the unit pricing before they decide to purchase a particular product or do they ...
512 views

### Statistical significance of a survey/poll?

Let's pretend I'm conducting a poll/survey. It's a simple yes/no poll (i.e. everyone only gives 1 of 2 answers). I have asked N people so far, and X of them have said "yes". I would like to stop ...
93 views

### Finding k-representatives from a 2 dimensional data set

I have a data set for second hand vehicle sales with 2 variables price and kms covered. If we plot these data in a 2-dimensional plane, the points will form scattered chart. I would like to select k ...
1k views

### How to compute margin of error with a given confidence interval?

I was given the following question: A survey found that 89% of a random sample of 1024 American adults approved of cloning endangered animals. Find the margin of error for this survey if we want 90% ...
476 views

### Percent error or percent difference?

Using either percent error or percent difference, I want to compare one of my measured values from a set to the mean of the set. By reading the Wikipedia article on percent difference, it's still not ...
416 views

### Should I use an average ECDF?

This relates to a previous question of mine which didn't gain many responses, perhaps because it wasn't very clear nd well written. I hope this time I will be more accurate and get your much ...
23 views

### Sample size calculation for comparison of 3 proportions

How do I calculate sample size for estimating difference in proportions between 3 groups? Most of the free sample size calculators have options for only 2 groups.
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### How to impute or predict a characteristic when one of the IVs in the prediction is other household members having that same characteristic?

In some data set A, we have: household id, person id, age, sex, and then a simple binary likes donuts / does not like donuts variable. In some other data set B, we ...
140 views

### Sample size for multiple linear regression

I have two questions : I am wondering if it is possible to know the size of the sample (n) for a multiple linear regression if I want the tests to be powerful enough ? To me, it seems very difficult ...
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### Sampling small dataset from large dataset with reference to a given variable

Here is a statistics question which I have been thinking about while working with some of my data. I have a large dataset named "bigbird" (say about a billion rows) and I want to randomly sample a ...
152 views

### clustered-stratified random sampling

i've got questions about clustered-stratified random sampling. let's say I want to do a research in narcotics. the population that I will be working with is a combination of academics, students, and ...
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### How many measurements (10 million molecules each time) are needed to analyze 15 million unique molecues in a 20 million pool?

This is my homework: There are 20 million DNA molecules in a library for high throughput DNA sequencing, each sequencing run can generate 10 million reads (i.e., analyze 10 millions of DNA molecules), ...
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### Is there any proper way to fix a sample to adjust for known demographic overrepresentation?

My spouse frequently works with (expensive, hard to obtain) data samples; for example route information for commuting bicyclists collected using a smartphone app. More often than not, these samples ...
80 views

### What alternatives are there for dataset reduction beside the random sampling?

I have 3 millions instances with 30 features each and I am trying to reduce it in a sensible size for my computer for a classification problem. What are possible methods I can use to reduce the data ...
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### Statistical test to find variable causing failure

I have a database with tests that are either a pass or fail and around 25 description fields. Each description field is either a boolean or has between 3 and 10 options. I'd like to hook into my ...
269 views

### What are the rules / guidelines for downsampling?

I have a data set with ~ 7 million rows, of which ~ 100k are positives. I'm looking to shrink the data by keeping all the ...
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### How many data points for my new product do I need to tell if my new product performs differently to the old?

We've been using the old formula to produce a product for years. We take a sample every quarter or so and run it through 8 different quality tests (every quarter because it takes that long for the ...
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### Help required with using the correct model for sampling

I regularly encounter the following scenario: I am presented with a set, $\mathcal{S}$, of $i$ items. I am assured that $d$ of the $i$ items possess a particular property, $d'$ - and that the rest, ...
119 views

### Sampling extremely large and diverse dataset?

General theories would be great. My specific problem is I'm trying to find a specific portfolio of all the stocks in the market. The possibilities are huge because I need the stock combination(itself ...
128 views

### Sampling from kNN density estimate

Is there an easy/standard way of sampling from a density estimated by kNN? I've searched online but I can't seem to find how to do this. Any links or methods pointing me in the right direction would ...
277 views

### How to sample clustering to estimate precision and recall?

There is a system containing $N$ clusters and in each cluster there are some elements. The clusters' sizes varies dramatically and most of the clusters are singletons. I need to know the precision ...
527 views

### Orthogonal sampling, latin hypercubes and low discrepancy sequences

What is the difference between each of them? this wiki page - http://en.wikipedia.org/wiki/Latin_hypercube_sampling says that: "In Orthogonal Sampling, the sample space is divided into equally ...
190 views

### Sampling dataset, choosing among N dimensions

I'm new in stats, and maybe this is a duplicated question, but I could not find a similar one. I'm trying to reduce a dimension of my dataset. Maybe reduce is not a good word. I need to sample some ...