# confidence interval

1. ### Comparing confidence intervals: CI of mean vs CI of regression coefficient

Hi, I have longitudinal data with measurements at two timepoints. I am interested in the change per year and calculated this in two ways: * Dividing the difference between the measurements by the time difference and averaging over all cases. * Performing a linear regression with subject...
2. ### Null hypothesis

4. http://i42.tinypic.com/2woyqgz.png 10. A physician claims that as soon as his patients have a positive pregnancy test, he is generally able to predict the sex of the baby and that his probability of being right is greater than the one-half that would be expected if he were just guessing. A...
3. ### Uncertainty in Standard Deviation

The 95% confidence intervals for the standard deviation (SD) of 5 measurements is approximately 0.6*SD to 2.87*SD. The measurements are laser analyses to determine the atomic composition of a solid material. If each of the 5 measurements, stated above, actually consist of the average of 50...
4. ### Calculating 95% confidence interval from mean, SD and number of subjects

Dear All I have been asked to present some information from a series of published articles according to Mean (+/- 95% Confidence Interval). The statistical summaries are generally presented as: Number of subjects (n) Mean (X) Standard deviation of the mean (sd) How do I calculate the...
5. ### confidence intervals for linear regression

Hi, newbie here, so please forgive the bad terminology. I started with ten years of historical data. I used Excel to give me a linear trendline and equation. I used that equation to get the forecasted data points for the following ten years. So far so good. Now I want to get the data...
6. ### Seek confirmation for robust approach of describing non-parametric data set:confused:

I’ve spent considerable time researching (on this site and elsewhere) for an appropriate statistical descriptor for a non-parametric (non-normally distributed) data set. I think I have the answer but would love any feedback as this is not an area of strength for me. TASK / DATA DESCRIPTION...
7. ### Confidence intervals for difference between change scores

Hi All, I have two groups tested at four timepoints with a survey of ability. I have compared the groups for change from baseline at each timepoint and have confidence intervals for each change score. Now i want to compare the change scores between each group. Obviously subtracting change...
8. ### [Paired T-Test] Assumptions & Violations

poor design methods
9. ### confidence band from se in quadratic regression

Hi, I have the following problem: I want to draw confidence band for a quadratic regression I have the model: y=a+b*x+c*x^2, i have estimation for a,b and c together with their standard error. how do i draw the confidence band. i sort of understand their should be 2 formulas, one for...
10. ### Bootstrapping confidence intervals for prediction based on SE of the coefficients?

Is it remotely legitimate to use the standard errors of the coefficients from linear regression in a Monte Carlo simulation to bootstrap 2.5%/97.5% confidence intervals on the predictions? If so (or if not), is there any literature relevant to this approach?
11. ### Working with a distribution of outcomes from discrete events

Hello, I have a data series that result from a long (2,950) series of discrete events. Roughly half of the events ended with a value of exactly -1, the other half are continously distributed between 1 and positive infinity. There are no values between 1 and -1. A histogram would look...
12. ### Confidence intervals for survival estimates with combinations of risk factors

Dear all, I have time-to-event data for patients with epilepsy. We have produced a parsimonious multivariable model for this event and therefore can obtain the probability of the event at each recorded time point. In addition to this, we can work out the survival estimate at a time point...
13. ### Relavance of confidence interval in Relative Risk

What exactly the relavance of the confidence interval of a Relative Risk? heard that if the CI includes 1, then there is no statistically significant relative risk. in that case can we conclude that what ever the RR is purely due to chance and no risk at all. really needa help in this...
14. ### Impulse Response Functions

I have obtained point estimates for impulse response functions. How can I tell if it's values are significant?
15. ### Question on mathematical soundness of confidence interval data validity test

Hello, I have data with daily values for a measured parameter for an entire year. Often within any given month there are several days with missing values. I need to have data for this parameter on a daily basis, so I utilize a statistical method recommended to me by a graduate to...
16. ### Difference between standard deviation and standard error

Hi, what exactly is the difference between the SD and SE? I read through the wikipedia article but dont really understand the difference. Can anyone help? Cheers beginner