Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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.

0
votes
0answers
6 views

Find number of elements to check for finding false negative rate

I have 3500 pictures that were classified in four different possibilities of match: very low (16%), low (1%), high (30%), very high (53%) All labels are not known, i.e., I don't know if they were ...
-1
votes
0answers
12 views

Are two samples from the same population/Is there a difference between these two samples?

I have two vectors about claim frequency (using an insurance context) e.g. V1= (.25,249,.34,.29,...) V2= (.278,.2997,.3,.23,...) I wanna test if there's a real difference between these two ...
0
votes
1answer
54 views

Multiple linear regression: am I interpreting the methodology right?

This is a follow-up question to 1 and 2. So we have the normal linear model \begin{align*} \textbf{Y} = \textbf{X}\beta + \epsilon \end{align*} where $\epsilon\sim\mathcal{N}(\textbf{0},\sigma^{2}\...
0
votes
2answers
32 views

What exactly is the sample size of an investigation?

My understanding of sample size is that it is a portion of the population that serves to represent the population. However, I'm not sure if the sample size of an investigation to investigate how X ...
0
votes
1answer
22 views

What is the sample size formula which i could possibly get minimum value in-vivo studies?

I am an undergraduate students who is struggling on how to do in vivo studies with my low budget. Therefore, I ask some help of you just in case you know about what sample size formula that I could ...
0
votes
0answers
12 views

How to infer the distribution of a statistic (Bayesian inference?)

I have a list of approximately 30,000 venues in a major US city. These venues hold all kinds of events, sports, conferences, concerts etc. I want to know the distribution of the 'capacity' of these ...
0
votes
0answers
17 views

Estimate frequency based on given sample

I have a list of users (~25 million) and a dataset containing events created by the users in a specific time window (eg all tweets of all Twitter users that happened in a month - on avg I have 100K ...
13
votes
3answers
2k views

Using mean length and mean weight to calculate mean BMI?

Is it valid to use mean length ($h$) and mean weight ($w$)) from a given population to calculate mean Body Mass Index ($BMI = \frac{w}{h^2}$) for that population?
0
votes
0answers
14 views

A question about power for a cohort study

In short, we are planing a cohort study, were we want to investigate the occurrence and the importance of a given event on response of a treatment. We expect the event to occur in about 2% of all the ...
0
votes
0answers
23 views

Is there any way to resample in order to change the distribution of a sample?

I ran an experiment that involved an independent variable which is known to have a right skewed distribution. However, in the experiment, the independent variable was distributed differently between ...
2
votes
3answers
331 views

How to figure out whether the data is sample data or population data apart from the client's information?

What are the ways available to figure out whether the data is sample data or population data apart from the client's information?
2
votes
1answer
42 views

Calculating required sample size for estimate lower bound on 95% of the population

I'm interested into sampling from a population, with a long time to get a sample (O(1), usually 1/2 mins), with lots of candidate populations to sample from (running a metaheuristic optimization). I ...
0
votes
1answer
14 views

Testing whether two timeseries samples are from the same population

I would like to test if different timeseries samples (over the same period of time) are plausibly from the same population. e.g. popularity of movie Avengers over time from different websites. The ...
1
vote
0answers
158 views

Calculating a sample size based on the target width of a confidence interval with stratification

I am reviewing a sampling design devised by a colleague and completely fail to understand it, although I am not a novice in statistics (but not a huge expert either). The said colleague is no longer ...
1
vote
0answers
28 views

Sample from a distribution constructed by Dirac measures

I am reading the paper in the following link https://link.springer.com/article/10.1007/s11203-009-9037-8 In the page 19, the author suggests to sample $\eta_i$ from the following distribution $P^{\...
2
votes
0answers
18 views

Unbiased Estimator of the Standard Deviation of the Sample Standard Deviation

I'm looking for an unbiased estimator of the standard deviation $\text{SD}(s)$ of the sample standard deviation $s = \sqrt{\frac{1}{n-1} \sum_{i=1}^{n} (x_i - \overline{x})^2}$. I have found this ...
0
votes
0answers
27 views

A question about the definition of sample

Let $(\Omega,\Sigma,\mu)$ be a measure space. The definition of a sample is that it is a sequence of iid random variables $X_1,\ldots,X_n$. Usually random variables are real valued and the ...
0
votes
1answer
32 views

How exactly can I get sampling distribution of means for calculation of standard error?

Let's denote population by $ N $ and sample with which I want to make inference about $ N $ denote by $ n $. Let's assume I have already collected $ n $. Now I want to get means for sampling ...
1
vote
1answer
30 views

Probability density of the product of independent identically distributed random variables

Let $X_1, X_2, \dots , X_n$ be a random sample from the PDF $$f(x;\theta)=\theta x^{\theta -1},\;\; 0<x<1,\;\; \theta > 0$$ What is the probabilty that $\prod_{i=1}^n X_i > t$? The joint ...
2
votes
1answer
30 views

Standard error of sample variance

We know that an unbiased estimator of the variance is: $$ \hat{\sigma}^2_{unbiased} = \frac{1}{n-1}\sum_{i=1}^n (x_i - \bar{x})^2$$ I was wondering, does it have the smallest possible standard error? ...
0
votes
1answer
43 views

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 ...
0
votes
1answer
15 views

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. ...
0
votes
1answer
28 views

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 ...
1
vote
2answers
51 views

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 ...
-1
votes
1answer
38 views

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: ...
0
votes
1answer
14 views

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 ...
1
vote
1answer
23 views

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 ...
0
votes
0answers
17 views

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 ...
5
votes
1answer
44 views

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 ...
0
votes
0answers
9 views

Conditional Probability Based on Sample When Population is Known

I have a count from each U.S. state of people that ride bikes. I want to know whether the count is larger or smaller than expected relevant to the population of each state (I also have the population ...
0
votes
1answer
61 views

Deciding on population vs. sample

I have been researching when to classify a dataset as population vs. sample for many hours now for a statistics project I am doing. I have a dataset of NFL combine data and one thing I need to clarify ...
0
votes
0answers
45 views

Calculating sample size for one 5-point likert item

I am trying to calculate the optimal sample size for a hypothetical experiment with the following: Treatment condition (n TBD) Control condition (n TBD) My dependent variable is an 'intent score' ...
0
votes
1answer
26 views

Evaluate Sample Representativeness of Dataset

I'm trying to check / evaluate how representative a sample is from a dataset. I'm interested in two things: Which sample best represents the original dataset Is the sample a "good enough" ...
0
votes
0answers
17 views

Web Based Survey Sampling method

I am doing a web based research with target audience as general public. I am a student and so due to limited resource, i basically did snowball sampling. I approached all those whom i knew, some ...
0
votes
1answer
31 views

Difference Between Notation of Two Sample Hypothesis Tests

Does this hypothesis test: H0: μd = 0 H1: μd ≠ 0 Represent the same as this test: H0: μ1 = μ2 H1: μ1 ≠ μ2 Since the first is asking if there is a difference between the true mean of the two ...
0
votes
0answers
10 views

How to create a scale combining normalized percentile scores to get an overall result

I am trying to work out a scale for assessing a person’s risk for a particular behavior (like rob a bank). The likelihood of this behavior occurring or not occurring will be based on scores for a ...
0
votes
0answers
5 views

Weighting cases if some population groups are missing in a sample

A usual way to weight cases in a sample for the $i$ category is taking its weight as $w_i$ = $P_i/p_i$, where $P_i$ is known proportion for that category in the population and $p_i$ – in the sample. ...
0
votes
1answer
23 views

what does that mean by saying “a sample having 2 (or more) observations”? does the observation mean possible outcome from an experiment?

Say, I am drawing balls. "drawing 2 balls from 3(labeled numbers from 1 to 3) with replacement" is an experiment. perform this experiment could result 9 possible outcomes. here is the list ...
0
votes
0answers
10 views

Location level a/b testing sample size

We are setting up experiments to measure impact on the city level. Customer in certain cities are treated and we have list of holdout cities with similar behavior. Measurement of lift of the ...
0
votes
1answer
41 views

Independent or Dependent sample

I am comparing whether Spot Gold prices and Gold ETF prices have the same performance. A spot price is the current price in the Precious Metals marketplace at which a given asset such as a security, ...
0
votes
1answer
29 views

R Calculate sample weights based on two socio-demographic variables and aggregate results

After conducting a short survey, I have collected the results in the form of a dataframe. This is a reproducible version of what the actual data frame looks like. ...
1
vote
1answer
28 views

Find significance between two group proportions

My question is the following: what statistical test would I use to compare the proportion of participants between two groups. For example, if in 2009, 20% of participants ( population was 55) to a ...
0
votes
0answers
13 views

Plotting groups of sample distributions as CDF with dispersion

Context I repeatedly run an experiment each repetition of which results in a sample of observations that I assume follow some distribution. (It is not important here what the distribution represents.)...
0
votes
0answers
37 views

Effective Sample Size for Weighted Samples

I have an MCMC sampler with weighted samples and I want to compute effective sample size at every step to determine sample degeneracy. I am using the following formula: $ESS = \frac{(\sum_{i=1}^N{w_i}...
0
votes
0answers
26 views

Sample Calculation of Morisita's Overlap Index

I am actually a biologist who has as question regarding how to apply the Morisita's Overlap Index. I have been told to compare two plant species by using this index and 3 other variables for each ...
1
vote
0answers
14 views

What is the cost of reconstructing a discrete probability distribution, from samples, within a given error?

I'm aware that there are several methods to estimate the probability distribution from samples (e.g. density estimation methods). However, I haven't been able to find the actual asymptotic costs of ...
2
votes
0answers
36 views

Why is unbiased estimation from a sample only possible for certain properties?

I was thinking about finding some monotonic measure of entropy of a sample from a continuous distribution (2D, btw), but couldn't think of any such without making assumptions. Why is it that one can ...
0
votes
1answer
24 views

Help with psychological research for my dissertation?

1) Is median split effective to divide participants in 2 groups considering their scores on a scale? I am using PECK scale (Personal experience checlist) and i need to divide participants into minimum ...
1
vote
0answers
15 views

Dealing with non-representative samples of a larger population

I'm seeking some advice about a project that I am working on. In this project, my colleagues and I are planning on collecting a sample that is intended to be representative of the national adult ...
0
votes
1answer
16 views

How do I report a Friedman Test when the sample violates the assumption: 'Group is a random sample from the population'?

How do I report a Friedman Test when the sample violates the assumption: 'Group is a random sample from the population'? My study involves a group of participants receiving an intervention and a ...