Tagged Questions

0
votes
0answers
18 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 ...
4
votes
1answer
174 views

How do I calculate sample size so I can be confident that the sample mean approximates the population mean?

Unfortunately, it's a long while since I did statistics and despite reading & research I'm not 'confident' as to how to calculate this correctly. I would like to know the smallest sample size ...
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0answers
21 views

Sample size for Wilson's confidence interval

Consider a story ranking website in which the ranking is crowd sourced from the number of up votes and down votes received by a story. The score is computed as the lower bound Wilson's algorithm. ...
3
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2answers
119 views

How does the confidence interval for the parameter p of a bernoulli trial vary with the value of p itself?

This is a very basic question (I'm currently studying undergrad level statistics), but I was hoping for some clarification regarding an assertion I read in a newspaper article earlier today. The ...
0
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0answers
248 views

How to quantify the significance of the difference between two z-scores?

I have one sample and several features. I calculate a z-score for various features, and for various combinations of features. Is there a way to quantify the significance of the difference between ...
0
votes
0answers
45 views

How big is n in a weighted portfolio?

I want to identify the relevance of some results. So far I have done some reading and have understood the following: I'd like to prove the meaning from my final results, and I want to evaluate the ...
1
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0answers
90 views

Minimum sample size determination for difference of two normally distributed populations

This is homework, but I am rather stuck and the TA for the class has yet to make his solutions. Any help with moving me in the proper direction would be most appreciated. I am having some difficulty ...
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 ...
2
votes
0answers
30 views

How is it that the required sample size for a specified error and confidence is not dependent on population size? [duplicate]

Possible Duplicate: Why does standard error not involve population size? When calculating confidence intervals for population parameters, the population size is never a factor, rather ...
6
votes
3answers
609 views

Confidence intervals vs sample size?

I am totally new to stats and the field of confidence intervals. So this might be very trivial or even sound stupid. I would appreciate if you could help me understand or point me to some ...
3
votes
2answers
112 views

Sample size when one hypothesis is overwhelming

I am looking at a situation where I have a population of about 150-170. I am testing for the absence or presence of a particular property. Given the population, I can easily figure out the sample size ...
2
votes
2answers
417 views

Can I compute a confidence level for a z-test based on the size of the samples?

I'm doing a two sample z-test for the difference between means using pooled variance. Suppose I've run two experiments. In the first experiment, the sample size for the two populations is only 100, ...
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 ...
3
votes
2answers
291 views

How to adjust average rating for sample size on rating systems with more than two categories?

After reading How Not To Sort By Average Rating which deals with confidence interval for a Bernoulli parameter how would you extend it to more than two levels? For example: Items are scored between 1 ...
2
votes
0answers
138 views

How do I compute a confidence level for a forced ranking survey?

How do I compute a confidence level for a forced ranking survey? For example, say I have 10 categories, each with four associated statements that must be ranked either 1, 2, 3 or 4 with no duplicate ...
2
votes
0answers
77 views

Significance of multinomial data [duplicate]

Possible Duplicate: Sample size for a variable number of answers I have data which was generated from a (theoretical) multinomial distribution, and using the data points I estimate the ...
1
vote
2answers
869 views

Determining sample size for uniform distribution

May you help me to decide what is the minimal sample size for a uniform distributed sample. Assume that I've find the sample average, standard deviation and the $\alpha$.
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 ...
1
vote
3answers
390 views

Statistical significance when A/B test has multiple values

I'm sure this is a pretty standard statistics question, but I'm no expert... I'm running an A/B test on my website to see if a change results in users adding more content. So there are 2 basic ...
0
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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
725 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 ...