# Tagged Questions

26 views

### One sided confidence interval for the mean

I want to test the following hypothesis: $$H_0: \mu \geq \mu_0 \\ H_a: \mu < \mu_0.$$ I use one sample t-test: $$t_0 = \frac{\bar{X} - \mu_0}{S/\sqrt{n}}.$$ Since under the alternative we expect ...
34 views

### Calculate p values based on differences between bootstrapped 95% confidence intervals

I have bootstrapped model fits to some data from different three groups, using the $2.5$ and $97.5$ percentiles to generate a $95\%$ confidence interval. I know that if $95\%$ confidence intervals do ...
183 views

### Why is standard error sometimes used for “error bands” in plots?

It seems that often what someone really wants to plot is a confidence interval of some kind, but using SE for this purpose I think only ends up comprising something like a 68% confidence band. ...
29 views

### Interpretation of Kolmogorov-Smirnov Generated Distributions [duplicate]

Note that this question is posted in Cross Validated but as of this writing have received no replies. As a non-statistician, I need help in interpreting a distribution generated from KS. A customer ...
217 views

### Interpretation of Kolmogorov-Smirnov Critical Value Generated Distributions

As a non-statistician, I need help in interpreting a customer specified two-part reliability requirement that I think involves KS. Requirement Part 1 R[4 years] must be greater than or equal to 0.95 ...
81 views

### How to compare proportions, dependent samples with different sample size

I have a dataset size=8755 that has many missing values. If I remove all the missing values, the complete dataset has size=2986. I'm trying to compare the proportion of both dataset in order to ...
109 views

### Confidence interval vs Significance level question

Until now I thought that the significance level and the confidence interval were the complement of each other, i.e. when some question asked me to carry out a hypothesis test with a $p %$ significance ...
51 views

In Google's consumer survey product, they calculate confidence intervals using the Wilson score interval for the unweighted results. Does anyone know how they calculate the confidence interval after ...
258 views

### How is the 95% in 2 standard deviations above different than 95% confidence interval?

Is there a difference between the two uses of 95% in: mean + 2 standard deviations (statistically significant) confidence interval
59 views

### How to measure which program is faster than another in a statistically meaningful way?

I am trying to compare 2 computer programs, X and Y, for speed. I want to determine which one is faster. I could, for example, chronometer those programs 20 times, take the average and state that the ...
18 views

### Testing for difference between two percentages (using confidence intervals) [duplicate]

I wish to test for whether the difference between 2 percentages is significantly different. For each percentage there are associated confidence intervals, which I need to incorporate into the test (CI ...
65 views

### Confidence or prediction limits for significant difference between forecast and observation?

My task is to to forecast business data without advertising and compare the real observations (with advertising effect) to the forecasted values in order to measure the effect of advertising. I am ...
288 views

### Ratios of means - statistical comparison test using Fieller's theorem?

I would really appreciate any suggestions with the following data analysis issue. Please read till the end as the problem at first may appear trivial, but after much researching, I assure you it is ...
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### Deciding if my mutant strains are significantly different from my wild type from data measured over time or from gradients

I have a set of data which is the oxygen consumption of a wild type (WT) and a few mutants. I averaged the data and plotted graphs with each mutant and WT series and plotted a line of best fit. Is ...
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### How to find mean and standard deviation based on a given confidence interval?

If a 95% confidence interval for a population mean ranges from 200 to 240 (that is, LCL=200 and UCL=240). Then, the computed numerical values of sample mean, $\bar{x}$, and sample standard deviation ...
262 views

### Significant difference from regression confidence intervals

I have a question about statistical significance in relation to confidence intervals from linear regression. I'm obviously far from a stats expert, and I've been searching for the answer to this, ...
97 views

### Computing event rates given RR + CI and total sample size in each treatment group

I am looking at some data for the risk of mortality in patients undergoing treatment A vs treatment B and I am given the total number of patients in each treatment arm and the relative risk + ...
376 views

### Standard Error used in Hypothesis Testing and Confidence Interval construction

In the excellent Practical Statistics for Medical Research Douglas Altman writes in page 235: "Because the standard error used for calculating the confidence interval differs from that used in ...
93 views

### Error Bars for Peaks in Noisy Data

I'm doing an experiment where peaks in amplitude $A$ (the dependent variable) are expected as one varies the frequency $f$ (the independent variable). Based on our theoretical model, Away from the ...
125 views

### Formula for metrics shown in multivariate testing

In multivariate testing of full factorial combinations, how to calculate 'Chance to beat original' and 'Chance to beat all'. This is shown in Google website optimizer tool. I did some research and ...
137 views

### Measuring real advertising effect: control group issue

Background: The goal is to measure impact of advertising technique - retargeting. Retargeting is about showing related ads to prospects who add something to shopping cart but abandon it. We would be ...
326 views

### Determining statistical significance in election polls from the MoE / confidence interval

I am confused about how to determine statistical significance in election polls. I was taught that overlapping confidence intervals do not necessarily imply a statistically insignificant difference ...
272 views

### Is there a statistical significance in my paired sample data after performing Wilcoxon signed rank test?

I have a paired data consisting of $N$ = 421 samples. I would like to find out if there is statistical significance between the paired samples. Since, I do not know the underlying data distribution I ...
146 views

### How many user interactions do I need to perform search relevance experiment?

I know similar questions have been asked many times here. But I still don't get simple formula or idea how estimate this. I have site with traffic and I want to split portion of it to test new search ...
2k views

### Significant p-value and relative risk crossing 1

I am trying to convert results I am finding in scientific articles into relative risks so that I can compare studies in a meta analysis (if there is enough homogeneity in the studies). I came across ...
539 views

### Confidence interval and probability - where is the error in this statement?

If someone makes a statement like below: "Overall, nonsmokers exposed to environmental smoke had a relative risk of coronary heart disease of 1.25 (95 percent confidence interval, 1.17 to ...
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### 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, ...
958 views

### How to calculate margin of error for a binomial quality control experiment where only successes are observed (including FPC)?

Wikipedia's Margin of Error entry says that a random sample of size 400 will give a margin of error, at a 95% confidence level, of 0.98/20 or 0.049 - just under 5% given an infinite ...
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### Multiple regression: What to do when the intercept is not significant? [duplicate]

Possible Duplicate: When is it ok to remove the intercept in lm()? I have some regression output from R: ...
263 views

### Expectation of length of a confidence interval for a proportion

a) For a given significance-level $\alpha$, if we find $\mathop{\mathbb E}(b-a)$ such that $\mathbb P(a \leq X \leq b) \geq 1−\alpha$ for all possible values of $a$ and $b$, from the point of view of ...
827 views

### How to interpret 95%CI's in conjunction with significance tests for differences between group means?

I have data for two groups, and I am investigating if the two groups perform differently on a task. I have 95% CIs calculated by bootstrapping that give lower and upper bounds to mean point estimates ...
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### How to calculate confidence intervals for the percentage of people who will download a song on a website?

So let's say that I am trying to find confidence intervals for the percentage of people who will download a song on a website. We've had 1000 people visit the site in one year and 100 people ...
73 views

### Paired multiarm bandit

I have a set of independent experiments with different distributions and I'm trying to determine which has the highest mean payoff. I would like to treat this as a multi-arm bandit problem, but the ...
793 views

### How to calculate a 95% confidence interval from time data?

I have a few (e.g. 10) observations of travel times for a route. A commuter needs to arrive to his destination before t0 (given). I want to say: The commuter should depart before ...
358 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 ...