# Questions tagged [sampling]

Creating samples from a well-specified population using a probabilistic method and/or producing random numbers from a specified distribution. As this tag is ambiguous, please consider [survey-sampling] for the former and [monte-carlo] or [simulation] for the latter. For questions regarding creating random samples from known distributions, please consider using the [random-generation] tag.

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### Sampling without replacement - Normal sampling distribution [duplicate]

Most of the introductory stats textbooks, treat the sampling distribution of the mean as a normal distribution when sampling is done without replacement and n/N > 0.1. They just use of the finite ...
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### Number of bootstrap replicates versus number of simulations

I have some confusion over bootstrap simulation in R. Here is the question: I am asked to use the following parameters to produce simulation: 500 bootstrap replicates 1000 simulations Sample size of ...
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### How to deal with balanced training data and severely imbalanced testing data

My dataset is severely imbalanced, negative class is the majority and its records is almost 10000 larger than the positive class records. I'm using Python. Here's what I have already done: I used ...
36 views

### Sampling from specific distribution

Suppose I have two random variables $X$ and $Y$ that are independent. Also suppose that I can sample from $X+Y$ and $Y$. Is it possible to combine those two sampling algorithms to get samples for $X$.
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### How to estimate high end percentile (e.g. >90%)

Say my dataset is of size $N$, and I want to calculate the 90th percentile. Suppose $N$ is too large that I can't compute the percentile by going through the entire dataset, what is the best way to ...
36 views

### Training a probability density from realization data

I want to learn a function that estimates a probability density over some 3D volume. I have a neural network that would work for this task and I would readily be able to train it, if I had density ...
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### Estimator for repeated sampling and fitting

Say I have a Normal distribution $\mathcal{N_1}(\mu_1,\sigma_1)$. Now I will sample $N$ samples $X_1$ from this distribution, and use estimators for $\hat\mu_2$ and $\hat\sigma_2$ to fit a new ...
271 views

### expected value of sample median?

I am confused regarding a question I'm currently working on. how do I go about finding the expected value of a sample median? given that I have 10 balls of which 7 are no. 1's, 2 are no.2's and 1 ...
152 views

### Question on central limit theorem

I have a question regarding central limit theorem! I understand that as the sample size increases and gets large enough, the sampling distribution of the sample mean can said to be approximated by a ...
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### Which cumulative distribution of F(X) is equal to the cumulative distribution of its sample median (as sample statistics)

We consider random sampling from a population in which the variable of interest $X$ has some cumulative distribution $F$. Next, we consider a simple random sample of size $n, X_1,\ldots,X_n,$ which ...
184 views

### Simulating Random Strings using Binomial/Multinomial Distributions

I am simulating some DNA sequences (containing characters A, C, G, and T) in R through specifying i) the number of sequences to generate (num.seqs) ii) the length of the generated sequences (length....
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### How tailed area decided for hypothesis testing?

I have a doubt in basic hypothesis testing. Suppose I have a testing setup as below. I have assumed null hypothesis that my sampling distribution has $\mu = 60$, and I get a sample set with sample ...
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### what type of sample is this?

I have the folowing table: according to this example, there are 40 observations distributed over 10 stores and 4 weeks of the month. Objective: to make a sample of 90%, 80%, 75% and 50% of the 40 ...
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### How do I work out how many people would be selected in a specific age range by chance?

I have sampled individuals from 100 centres, all aged 5 to 7 years (a total of 1950 individuals). There were two groups that were sampled separately, at a higher rate: those aged 5 years and 11 ...
65 views