confidence intervals

  1. D

    Interpreting Results of Monte Carlo Simulation (R)

    Hello, I have conducted a Monte Carlo simulation in R based on the guidelines below and I am struggling to interpret my results. Consider the following data-generating process Y = β1 × X + u 1. Simulate 1000 samples of size n = 100 with β1 = 2, X ∼ N(100,15) and u ∼ N(0,8). 2. In each...
  2. S

    Intrabatch variabilty estimated from pooled SD and confidence intervals

    I would like to calculate intrabatch variability of parameter A, which is normally distributed. I have data of 50 batches (the same process), for each batch I have one representative sample with sample size = 10. I have calculated pooled SD from the samples of all 50 batches (I assume this is...
  3. O

    Bootstrap confidence intervals for an index calculated on counts

    Good morning! I would like to calculate 95% confidence limits for both lower and upper possible values of the Ivlev’s index as it has been done on the below screenshot from a paper of Hebda, Wesołowski & Rowiński (2017) in order to assess the significance of the index values for particular...
  4. S

    Calculating confidence intervals for monthly data

    Hello, I am currently working with monthly data and I try to calculate confidence intervals for the monthly average. I have data from from 2010 to 2019 and there seems to be some seasonality. The statement I want to make, is: In december 2020, we expect a value of x which lies with a certainty...
  5. M

    Confidence intervals exceeding 100% and going below 0% for mortality rates

    Hello, This is probably a very naïve question however, when plotting some graphs of mosquito mortality against different insecticide treatments I noticed the confidence intervals for some of the most effective treatments exceed 100% and that in the control they sometimes go below 0%. Firstly...
  6. M

    Why One Sample For Confidence Intervals?

    As I understand it, The Central Limit Theorem and Confidence Intervals are related. What is the best way to explain why the Confidence Interval formula uses only one sample whereas the Central Limit Theorem uses 'many' samples? Isn't the x-bar in the CI formula the mean of one sample? Don't we...
  7. G

    Construct a 95% confidence interval for the population proportion of all students...

    A researcher wants to know what proportion of all students who have completed a course in Statistics do not have a solid understanding of what a Sampling Distribution is. A random sample of 320 students who recently completed a Statistics course were given a basic exam on Sampling Distributions...
  8. T

    Confidence Intervals. Why Just One Sample?

    A typical problem in a Stat Textbook for creating a confidence Interval sounds like this: A sample of 50 blood pressures is taken and the sample has a mean of 120 with a standard deviation of 5. Construct a 95% confidence interval. What troubles me is that only one sample is enough. Intuitively...
  9. R

    Bayes - need help informing priors

    Hi! Anyone here familiar with Bayesian inference? I would like to inform priors for an analysis. I have Odds Ratios and 95% CIs. How would I calculate the variance from the CIs. I know how to calculate SEs, but I don't think that is the custom for priors (its usually mean and variance)...
  10. S

    Can someone please check my answers? It's over confidence intervals

    This isn't techinally homework. It's extra practice questions giving by my teacher. I just want to make sure I'm understanding everything correctly. If I have a question wrong, can you please give me the right answer and explain it in great detail? 1. Construct a 95 percent confidence...
  11. A

    Large Sample Confidence Interval for the Mean - Problem is it right ???

    The president of Jones Bank asked his research team to determine the average waiting time for its customer. A study of 100 customers was conducted with the following results: mean = 19.8 standard deviation = 2.06 minutes Prepare the 95% confidence interval for average waiting time... mean =...
  12. C

    Equivalency testing - CI approach and TOST don't match

    Hey everyone, I'm doing some equivalency testing with both the CI approach and TOST to demostrate the equivalency of two scanning methods. For most of my samples, results align as one would expect, i.e. if the CI lies within the upper and lower bounds, the p-values calculated with two...
  13. L

    Confidence Intervals in a research paper

    Hi, all. I'm writing a paper on concussion data from the NFL Surveillance System, and I want to be able to put the data analysis from the journal article in my own words, but I don't really understand what the researchers are saying. Here's the quote. Can someone please tell me basically what it...
  14. P

    False Coverage Rate - adjusting confidence intervals for multiple comparisons

    Hello, I could do with some help regarding correcting confidence intervals for multiple comparisons. I have carried out a number of multiple regression analyses, which has given me various different p values. I have used the Benjamini Hochberg procedure to determine which p values survive...
  15. T

    please help me justify sample size for a pilot clinical trial

    I'm a bit desperate for statistical help so trying out all avenues. Any guidance appreciated! I need to justify a sample size of 30 or 32 (15 or 16 per arm) for a placebo-controlled pilot clinical trial of a drug. This is all I can afford, but that is not a good enough justification for...
  16. R

    Data analysis

    I have been asked to analyse the following data using linear analysis, mean standard deviation and ANOVA. However the data presented is supposed to be continuous but for small values they have grouped them as less then 5 almost like discrete. They represent the ages of children using...
  17. P

    Inaccuracy of Non-Parametric Bootstrap for great sample sizes in Excel-VBA

    My aim is to evaluate the performance of parametric and non-parametric Bootstrap under specific circumstances; and particularly their ability to capture the population mean within their produced confidence intervals -from now and on when talking about "coverage" I mean the ability of the...
  18. K

    confidence intervals for correlations on AMOS or SPSS

    Hello, I was wondering how to calculate confidence intervals for a correlation coefficient on Amos or SPSS. I've been trying to do it on SPSS by standardizing my data, but i've been told the estimate is not fully accurate. When i try to do it on Amos, i get the correlation coefficient but no...
  19. K

    Trimmed Spearman_karber Method using r for dose response analysis - Help needed!!!

    Please could anyone show me how to go about using r to LC50 and Confidence intervals with Trimmed Spearman-Karber method? I have had several go at the codes provided online (e.g, shown below) but couldn't make any progress. I loaded the package "drc" on r and yet couldn't find my way in using...
  20. D

    Confidence interval for person time incidence rate

    Dear everyone, I would like to estimate a 95%CI of person time incidence rate (as 45 death per 10,000 person year) Anyone knows a way to estimate it ? Same question for Kaplan Meier estimate.. Thanks a lot for your help!