# Questions tagged [sample]

A sample is a subset of a population. Statistics, in general, is concerned with using samples to make inference about the parameters governing a larger (possibly infinite) population.

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### Determine sample size using reversed goodness of fit

I am asked to work on a specific problem in which I have to calculate certain expenditures for an industry, consisting of a population of about 400 companies. Although I already suggested to conduct a ...
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### Proof that covariance of RV and group average is less than variance of RV

I have a random variable $X_i$ and a group of $N_j$ other random variables that includes $X_i$. Let's just call this group $J$. There are no distributional assumptions made on these RVs (other than ...
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### Different sample size of control and test groups

Hope someone can help my question: I have a survey study with one control group and one test group. Each is set to have 500 completes. However, we are short in sample in one group: Test is 350 and ...
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### Infering population from a sample?

I took a test in class and found it to be difficult. So I asked in my WhatsApp group if others felt the same. 4/36 people replied yes they felt it difficult. Others did not respond either in yes or no....
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### How to calculate the Margin of Error in this specific scenario?

Assuming I have a population made of hotel bookings for a specific period and I need to send a survey questionnaire to each guest (guest=booking) by email. To simplify things, let us assume the ...
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### Confidence Interval for the Difference Between Proportions in complex samples

I have two complex samples (with different sizes) from the same population in different times. I used the survey package to create designs for them: ...
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### Calculate a Conditional Expectation via Samples

Consider a binary random variable $Y \sim p(Y)$, a random variable $X \sim p(X)$ (can be discrete or continuous) and a conditional distribution $p(X|Y)$. Suppose that I generate $N$ samples from $p(Y)$...
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### intuition behind SD+

so i was reading statistics by Freedman and in the section where he describes the t-test he goes on to explain why we would use the SD+ instead of the regular SD to calculate the S.E with the sample ...
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### How do I sample N items from a list ensuring the samples are as similar as possible to each other?

Is there anyway to sample 6 numbers without replacement this list of 12 numbers ...
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### 2x3 design, binary out come sample size calculation?

I'm designing an experiment as part of a marketing assignment. I'm planning on running a 2*3 between-subjects design (6 conditions comprised of two factors, one with 2 levels and one with 3 levels). ...
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### Sample is almost the same as the population

I'm interested in a situation where I have a small list of events, somewhere in the range ten to a few hundred. Each event can be a 1 or 0 outcome. I have a good reason to believe that the factors ...
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### What distance function to use for matching observations on a mix of ordinal, nominal and numeric variables?

I'm trying to match potential respondents to a random sample from the target population, and not sure whether any of the usual methods available out-of-the-box in e.g. R are right for the job. ...
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### Problem on conducting a hypothesis test with sample data

I'm trying to perform a statistical tests for the sample data(n=63) which is the effect of smoking for time(measured in minute) to fall asleep. First, I set a null hypothesis, there's no effect of ...
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### Hypergeometric Probability with a twist

A manufacture receives a lot of 200 parts from vendor. The lot will be unacceptable : If more than five (>5) parts are defective. The manufacturer will select randomly K parts from the lot ...
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### Sample size (CI 95%)

I have two groups (treatment and placebo) and for each group I have the 95% CI mean calculated as per here. I want to do the same for calculating the 95% sample size as per table 11 of this paper: ...
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### How to decide sample size for validation?

I have data having over 20000 rows. 1) I am going to use a tool to test how many error rates this tool will calculate in this data. 2) And then, I will randomly choose some data and check how many ...
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### Favorite sequence in 10 flip tosses

I have the following question. Somebody likes to flip coins. In particular, this person is delighted to get a sequence HTTH. Assuming the person flipped coins 10 times, what is the probability that ...
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### Minimum Sample Size for M&A Event Study

as statistics beginner I was hoping you could help me with regards to the following problem: I wanna conduct an event study (analysing abnormal returns of share prices) to derive performance effects ...
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### What does the distribution of samples from an MCMC method converge to without repeated samples?

Suppose I have an absolutely continuous distribution with density $f(x)$ and I use an mcmc sampler which has accept/reject step to sample from this distribution. In the final samples, there are some ...