confidence intervals

  1. J

    Confidence Interval homework help

    This is the only part of our homework I am not understanding... A.)If the 95% confidence interval for the population mean is (6,20), what is the sample mean? B.)Given the 95% CI in part a, would (5,21) be a possible 99% CI for the same sample of data? If not, why not? C.)Given the 95%...
  2. D

    Pearsons correlation, confidence intervals, bootstrapping... Statistical nightmare

    I am currently running a project where I have 4 variables and a questionannaire with 4 subscales. I have performed a Pearsons correlation on this (due to high frequency of extreme scores in the questionairre and non-normal distribution of the questionnaire) and have found 2 significant results...
  3. K

    Multilevel meta-analysis in R using lme4 and lmer

    Dear users, I am running multilevel meta-analyses in R using lme4 and lmer. lmer(effect size ~ -1 + Covariate + (1|StudyID), data = data, weights = weights) My question is – is there a way to calculate confidence intervals that takes into account the fact that some effects are nested...
  4. F

    How to calculate the confidence interval of the ratio of two means (paired data)

    Hi there, I am writing a systematic review and need to calculate the 95% confidence intervals of the ratio of means from whatever the clinical trials I'm reviewing give me. The problem is: none of the studies actually report this information, and all I am given usually is the mean...
  5. J

    Confidence intervals: normal vs t-distribution (central limit theorem)

    Hi all! We did a serological survey for a disease taking 300 samples in a population of 50 000. If our sample mean gives a 2% prevalence. How do we work out the confidence intervals? I have all the formula's and there are great CI calculators on the web BUT seeing that is only one survey...
  6. A

    help!! I have a test and none of this makes sense.

    Hello! I have an exam on inferential statistics, etc and need serious help.
  7. M

    Reaching a 95% Confidence level within an estimated population.

    How can I reach a 95% Confidence level after estimating the population size? I have a population of 367 products of which I have a sample of 50. Products can have a damaged package or can be damaged itself. We know for a fact that products can only be damaged if the package is damaged. From the...
  8. M

    Non-Parametric Analyses. Report medians and 95% CI in graphs?

    Okay so, I'm currently writing my thesis, and I have to do non-parametric tests. I know that I have to report the medians in text. However, I'm doing graphs. Just wanted to ask whether anyone knows if I report the 95% CI and the medians in the graphs? When i do this it looks super weird and...
  9. H

    Probability that Bernoulli p-parameter is greater than some value, given N samples?

    Hello everybody, I have the following question. Assume I observe N outcomes from a Bernoulli random variable with unknown success parameter p. Based on these outcomes (or samples), how likely is it that the real parameter p is larger (or smaller) than a given value eps (e.g., 1%)? Any...
  10. C

    Clarification on Error Propagation

    I thought I understood the basic operations for error propagation (addition, multiplication, etc), but I have a few questions: 1. Is variance the only measure you can use? I only have 95% CI available to me. 2. Does multiplying/dividing a mean +/- CI by a constant preserve the error (ie CI...
  11. M

    Confidence intervals for eta squared?

    Hello, is it possible to calculate confidence intervals for eta-squared manually? I found a paper which lists the formula for this: http://www.jstatsoft.org/v20/i08/paper (pages 12 and 13), but the paper doesn't say how to calculate ^L and ^D, which are a part of the formula. Can anyone please...
  12. O

    Help with confidence interval and interpreting data!?

    Someone please please help me make sense of these stats! I really need help with interpreting outcome of studies! How do i calculate CIs (no need to know actual calculation as can use calculator) and make sense of outcome... Any help would make me forever grateful! STUDY 1. Pre- and...
  13. A

    Determining an indirect confidence interval for justifying a non-inferiority margin

    I need to establish the efficacy of a test treatment (T) by means of an indirect comparison to placebo (P). Therefore a study of T vs. reference (R) will be performed, and there is 'historical' data for the comparison between R and P. The outcome measure of interest is a responder rate (i.e...
  14. D

    Does Sqrt of confidence intervals require a correction factor?

    I have the following formula for confidence intervals on samples from a Rayleigh process: \frac{2(n-1)\overline{r^2}}{\chi_2^2} \leq \widehat{\sigma^2} \leq \frac{2(n-1)\overline{r^2}}{\chi_1^2} I want to give confidence intervals in terms of \sigma, not \sigma^2. If [x, y] are the 95%...
  15. H

    Need help: Can i genaralize to the population, or do i have to weight my data?

    I have a sample of 194 households from 3 villages. The number of hh from each village is 61, 67 and 66. I used a 90% confidence level and 10% margin of error to determine sample sizes. (total household population for all three villages is 4194 households). The total sample size for all three...
  16. M

    95% Confidence Interval for Regression Coefficients Question

    Hello all, I have been trying to figure out how to answer these homework questions for far too long and happened upon this forum with hopes that I could get a nudge in the right direction…Here is the problem as an attachment. Also included is my work thus far…I think my issue is...
  17. N

    Confidence Intervals for r: Why must we standardize?

    Hello! I know we are supposed to convert our r-values to z-values (and standard error) in order to calculate confidence intervals. I am a bit confused why we must do this. The sampling distribution for Pearson's r is a t-distribution and we use a t-crit in confidence intervals when our N...
  18. P

    [SaTScan] relative risk confidence interval calculation

    Thank you for reading this. My question is regards the methodology used by SatScan for purely temporal cluster analysis using a discrete Poisson model satScan's output gives me the following: How do I calculate confidence intervals around the relative risk? Thank you!
  19. T

    Accounting for confidence intervals in determining a mean

    I have received some elemental analysis of a metal which I want to use to determine the effects of radiation. I want to report my results for the mean and 90% CL. The analysis only presents 8 data points for each element so I was planning on using the t distrobution as follows...
  20. M

    Statictics Assistance needed

    Hi Im really stuck with a particular question regarding calculating confidence intervals. I dont expect anyone to solve it for me but just a push in the right direction would help heaps :) Recent research published in the Proceedings of the National Academy of Sciences has examined whether...