Tagged Questions

0
votes
0answers
21 views

How to add confidence intervals to describe the variability in monthly samples of data?

The data analyzed here is a sample of individuals collected on a monthly basis. What would be the best way to compute confidence intervals for the monthly sample means, in order to indicate the ...
0
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0answers
85 views

Why does the mean of the bootstrapped distribution not equal the original summary stat?

I have n samples and their average. There's some correlation so I used a moving block bootstrap to get an empirical distribution of the mean. The mean of this empirical bootstrapped distribution seems ...
2
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0answers
28 views

seeking statistical measures to use when evaluating a facial photo's “quality”

I have a large set of facial photos and a facial feature finder which helps me locate faces with a general idea of the location of the eyes, nose, mouth, and a curve outlining the face. These facial ...
4
votes
1answer
50 views

What are the optimizations or goals to consider when using stratified sampling?

In stratified sampling, what are the optimization considerations? For example, the sample size per stratum could be defined with proportional allocation as $n_h=n\frac{N_h}{N}$, where $N_h$ is the ...
0
votes
1answer
181 views

How does confidence interval vary with sample size?

I am trying to convert state-level poll results for 2012 U.S. presidential election into state-level probabilities of each candidate winning. To achieve that, I am using the logistic function, which ...
4
votes
1answer
369 views

Minimum sample size to achieve a specific confidence level and interval

I am building software components that are going to be used by multiple users simultaneously. At the current point in time, these components are known bad. That is, if I simulate multiple users ...
2
votes
2answers
367 views

Sample size for binomial confidence interval

Background: A group at work is sampling 1,000 customers to contact and from that point, determining if the effort is worthwhile or not. I wanted to see if this (pretty much) arbitrary sample size ...
1
vote
1answer
54 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 ...
1
vote
1answer
71 views

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, ...
3
votes
1answer
200 views

Determining appropriate sample rate for count data

Context: I am collecting Twitter data through a source that allows me to take a statistical sample of tweets that match a filter. I want to determine the appropriate sample rate in order to achieve ...
2
votes
3answers
924 views

Interpreting a negative confidence limit for a proportion

The margin of error is driven by the size of the sample. In a consultant's report (which is confidential at this stage), they collected responses from 10 store managers (out of a total of 200 store ...
4
votes
2answers
227 views

Sample size for a variable number of answers

I have N different possible results (ex. red, yellow, or blue). I go to a population of infinite size and ask a bunch of people a question the answer to which is one of the N options.... How large ...
5
votes
2answers
332 views

Putting a confidence interval on the mean of a very rare event

I'm simulating an extremely rare event (the detection of weighted photon packets in a highly absorbing material). For example, I may simulate the transmission of 1e9 photons and only detect 10 of them ...
4
votes
0answers
338 views

Sample size to achieve given confidence level

I am trying to estimate number of different unique visitors who visited a given website (online store). There are hundreds of millions of visits to the store and so this task is too difficult to ...
0
votes
0answers
134 views

Sample size needed to find all error values

This is a pretty basic question as I'm new to stats, but hopefully someone can help! I have a sample size of 30,000 records and so far 6500 have been checked to see if an error exists - of these ...
3
votes
1answer
726 views

How to calculate confidence interval when only a part of the samples are valid?

I will simplify our problem in this way. Say there are 100,000 cases in total to examine. Due to the time limitation, we randomly selected 2,000 of them. Then we found 1,000 of them are invalid, so we ...