Questions about the statistical process of sampling from a population, in order to obtain information for use in statistical learning, estimation, hypothesis testing about some population or process. Use this tag along with the tags (probability), (probability-theory) or (statistics).
Questions tagged [sampling]
1377 questions
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How many words do I know, extrapolated from a sample?
I would like to check my knowledge of foreign words by sampling a N words dictionnary: after checking randomly n words I would find that I know k of them (and do not know n-k).
How should I choose n so that the sampling is representative (= so that…
WoJ
- 836
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Independent sampling with at least two elements, without re-sampling
Suppose we have a sequence of numbers (WLOG, $[n]$) and we want to sample elements from it into a set $S$, where each element is sampled independently at random with $p_i := \Pr[i \in S] \in (0, 1), \forall i \in [n]$.
We do this multiple times, and…
Vezen BU
- 1,963
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Using distribution of sample mean to find expected value, variance, bias and MSE of sample mean
a) Determine the values of the population mean and the population variance.
b) Suppose we use an SRSWOR of size $n=4$, list all the possible samples of size $4$. What is the probability for each sample to be selected? Determine the distribution of…
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Intuition for the sampling weight to be the inverse of the probability of that unit being selected
What's the intuition for the sampling weight to be the inverse of the probability of that unit being selected? Here's an example of such a definition.
I would tend to think that if a unit has a higher chance of being selected, it should have a…
An old man in the sea.
- 5,241
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How to find all the possible samples of 3 from a population of 5 in Rstudio?
I'm trying to find all the possible samples of 3 of this population in Rstudio: 12, 12, 14, 15, 20.
I know by using the combination formula that it will be 10 of them. I want to find all the list using Rstudio. I tried to do it manually but I just…
bdvg2302
- 1,149
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Is PDF always given when we do sampling?
I studied "Inverse CDF method", "Rejection sampling".
So far, what I learned is that when we do sampling, the PDF is always given.
Is this true for all samping method?
Young Hyun Yoo
- 119
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Sample size to find a death rate
I need help, please, in working up a sample size. I’m working on a real project to track the incipient famine in Afghanistan by estimating crude death rates over time using survey data gathered from a sample of mosques. Enumerators will visit…
Sebastian
- 103
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How to sample a population based on an online survey form
I'm currently doing a research on TAM based on a prototype on my application. May I know how can I conduct a sampling on the data collected? (usually if interviews are conducted, we can randomly select respondents but in online environment, Im not…
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Variance property of a random sample
$X_1, \cdots ,X_n$ are a random sample from a population. $f(x)$ is a function such that $\mathrm{Var}$ $f(X_1)$ exists. I want to show that $$ \mathrm{Var} (\sum^n_{i=0} f(X_i) ) = n (\mathrm{Var} f(X_1)).$$
This is my attempt. …
Godwin
- 57
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Can one permute samples in Metropolis-Hastings to solve autocorrelation problem?
The wikipedia article on Metropolis-Hastings algorithm suggests that using all of the sample points produced by the algorithm as i.i.d samples from the underlying distribution is bad, since consecutive samples are autocorrelated. The article…
Aleksejs Fomins
- 2,240
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An experiment consists of rolling a fair die 100 times.
If this experiment is repeated, what is the sampling distribution of the proportion of the 100 tosses that land with one spot in the top face?
the P(getting a 1) = 1/6
how do I find the proportion value if idk how many times of getting a 1? do I…
Mia
- 23
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Sampling Problem with bottles of Cola.
I'm doing practice problems in my book to help me gain a better understanding.
The amount of cola in a 355 ml bottle from a certain company is a random variable with a mean of 355 ml and a standard deviation of 2 ml. For a sample of size 32, perform…
user839486
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Can someone help me understand the variance part of this theorem?
This is distribution of the sample mean when $\sigma$ is known
Theorem 6.1: Let $X_1, ..., X_n$ be a random sample from a distribution with mean $\mu$ and standard deviation $\sigma$
Then Var($\bar{X})$ = $\cfrac {\sigma^2}{n}$
Proof in the book: By…
user833797
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How to correctly sample lines from large file when order and lines count are unknown?
Input:
potentially large file with text lines
lines count is unknown, naive assumption gives range maybe more than 100K lines, but less than 400K
it's unknown if lines are sorted or not
it's fine to keep in memory at most 10.000…
Capacytron
- 113
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Finding largest viable step size, simple
I have a set of rational numbers $t_0, t_1, t_2,
\dots ,t_n$ in strictly ascending order $t_i < t_j$ where $i < j$.
My goal is to find the largest possible step size $\Delta t \in \mathbb Q$ such that for all $k$ there's a $c_k \in \mathbb N$ such…
Oria Gruber
- 12,739