Tagged Questions

3
votes
0answers
146 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 ...
1
vote
0answers
19 views

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 ...
-3
votes
1answer
62 views

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 ...
3
votes
1answer
120 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, ...
0
votes
0answers
33 views

A randomized block experiment [closed]

A randomized block experiment was conducted to investigate the effect of different lighting patterns (the treatment factor) on the egg production of chickens. Extended daylight (14 hours) and flashing ...
0
votes
0answers
42 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 + ...
1
vote
1answer
119 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 ...
3
votes
0answers
61 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 ...
0
votes
0answers
94 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 ...
2
votes
0answers
96 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 ...
0
votes
0answers
150 views

How to hand calculate parameter estimate, CI and wald test for a poisson regression that models $log\frac{\mu}{t}$?

I'm wondering if it's possible to hand calculate parameter estimate, CI and Wald test for a Poisson regression that models $log\frac{\mu}{t} = \alpha + log(t) + \beta(race)$. Given the Race 1's ...
2
votes
2answers
209 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 ...
0
votes
1answer
216 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 ...
1
vote
1answer
103 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. So I have site with traffic and I want to split portion of it to test new ...
3
votes
2answers
1k 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 ...
10
votes
5answers
463 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 ...
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, ...
2
votes
2answers
760 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 ...
1
vote
0answers
94 views

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: ...
3
votes
1answer
230 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 ...
4
votes
2answers
581 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 ...
0
votes
1answer
61 views

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 ...
2
votes
0answers
68 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 ...
2
votes
3answers
693 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 ...
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 ...
1
vote
3answers
389 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 ...
1
vote
0answers
84 views

Automation of standardization [closed]

Can anyone point towards applications, SQL algorithms or similar that automate the production of standarized rates/ratios (ie directly/indirectly age/sex etc.-standardized rates/ratios) with ...