# confidence interval

1. ### Confidence intervals from glmer models

Hi! When reading this, please keep in mind I'm pretty bad with statistics so please bear with me. So, I'm trying to analyse data from an ecotoxicological experiment. I have fish that were exposed to a substance during development and want to look at behavioural effects in the adult fish. I have...
2. ### Kaplan meier: hazard and 95CI

I have conducted a time to event analysis with the kaplan-meier method and my instructor requested for HR and 95%CI of specific time points such as 1 year or 3 years. However the life table in Kaplan-Meier analysis lists me the cumulative survival for time points at which last follow-up occured...
3. ### Am I understanding/describing this right? (chi sq, confidence intervals, ACE model)

The experiment is a twin study - using pairs of twins to investigate similarities and differences and look at how much genes and environment contribute to an outcome. The purpose of the study was to investigate the contribution of genetics, to attachment disorder. It was also to investigate...
4. ### Estimating location of lower tail

Say I have a sample, assumed from a Normal Distribution. I want to find a confidence interval for this parameter: L = \mu - \alpha * \sigma where \alpha is a known constant. I guess I should use the estimator: \bar{x} - \alpha*s But what standard error should I use? Just for...
5. ### Prediction Plot with CI's: What to do with covariates?

Hi, I have a multiple regression model (especially a GLMM), with - outcome Y, - a fixed effect predictor wich is in the main focus of my interest (time variable: "YEAR") - an additional fixed effect covariate, which is only in the model to prevent bias ("LOCATION" - the sampling...
6. ### Help with C.I. for non normal probability distribution Excercise

Hi! first time poster here! I have done (correctly I hope) most of the exercise except for segment "B) i)" So I need help with it :(:( Here's the exercise [What I've got so far] n = 10 A) sample mean (x) = 5.7 ; Std Deviation = 3.257 B) ii) Error = 2.0143 ; U € [3.685 ; 7.714] 95...
7. ### CI for Dependent Variable in Multiple Linear Regression

I have a regression model but I want to get a 95% confidence interval of the dependent variable for given values of the independent variables. I found that for a single factor regression: Confindence interval = t(alpha, DofF) * SYX * SQRT(1/n+(X-XAVG)^2/SSX) where n is the number of...
8. ### Confidence intervals for proportions: approximating a discrete distribution with a co

I saw on this website http://onlinestatbook.com/2/estimation/proportion_ci.html The following quote about calculating a CI for a proportion: Giving: p \pm Z_{.95}\sqrt{\frac{p(1-p)}{N}} \pm \frac{.5}{N} Where (it appears) N is the sample size. Another website...
9. ### Cox regression survival analysis

Hi, I am currently undertaking my dissertation and wondered if you could help me with some data analysis from one of my studies. The study indicates that they use Cox regression for survival analysis Results indicate that for group differences in depressive episodes the hazard ratio =0.38 95%...
10. ### Calculating the amount of underestimation

Coverage rate for a parameter is 91.2%, and the nominal coverage rate is 95%. If the confidence interval is based on asymptotic standard normal, then the amount of coverage 91.2% implies that the standard errors for the parameter is estimated about 15% too small. Because z* value used to make a...
11. ### Sampling Protocol and Relative Sampling Error

I’ve been racking my brain over what is likely a straightforward problem, but a little different than what I’m used to dealing with. I’ve got a sampling protocol I need to hit that states ”Confidence of the estimate should meet or exceed +/- 10% at one standard error”. I’m accustomed to...
12. ### Sample size - have searched high and low,bu tprobarbly very quick and easy to answer!

Hello Friends, I haven’t looked at a statistics book for a good 5 years, since leaving uni and moving into the job world. However, I have come across a real world problem where I feel there is a statistical method to help me, but after searching high and low cannot find it. I’ve looked at...
13. ### Non-para: "THE CONFIDENCE INTERVAL FOR MEDIAN BASED ON SIGN"

So my professor decided to write his own textbook, and we are finding errors everywhere, and it's difficult to understand, so I've tried google-ing and everywhere I go people are using different methods than the one he wants me to use here is an expample of what I am working with: 9. A...
14. ### Comparing a Binomial and Normal Distribution

So I'm currently analyzing several sets of data, that all represent the exact same type of data. There are multiple sets of this data, but however are in different forms. That is, some of this data is in the binary form, either presence of absence, while others are in the quantitative form. My...
15. ### How is the confidence interval for variance component in "lmer" function computed ?

Here is the R code : library(lme4) fm1 <- lmer(Reaction ~ Days + (Days | Subject), sleepstudy) confint.merMod(fm1,oldNames=FALSE) And the output is 2.5 % 97.5 % sd_(Intercept)|Subject 14.3814761 37.715996...
16. ### Confidence interval of parameters of mixed-model in R

Hi , can anyone please explain me the following output produces in R when I ran the command confint(lmer()) . Here is the R code : library(lme4) fm1 <- lmer(Reaction ~ Days + (Days | Subject), sleepstudy) confint(fm1) And the output is : Computing profile confidence...
17. ### Confidence level and Margin of Error applied to Satisfaction surveys

Hello, New to the forum, relatively new to stats as well! So I think I've managed to confuse myself and am going around in circles with this, so help would be appreciated. I'll outline what i'm trying to achieve and what data I have available below: So, i'm sending out satisfaction surveys...
18. ### 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...
19. ### Deducing Sample Size from Sample Proportion CI

How do I approach this problem? Suppose we want to estimate a sample proportion to within 0.05 with 95% confidence, how large will the sample have to be? There is no other information about the distributions of the population or the sample. No point in trying to solve for n in the...
20. ### how does stata calculate confidence intervals for age standardised means/proportions

Dear Stat Talkers! I'm using the following Stata command (see help mean): mean x, std(a) stdw(b) over(c) to get age-standardised mean or proportion of a variable of interest x. a= variable for age-group and b= variable for weights for each group. x can be a continuous variable or a...