confidence interval

  1. A

    plot mean value according to confidence interval

    Hi all, i have a very simple question, because i am not good at statistics but i need that :) I have two signals, one is lets say 'x' another is 'time', so its a time serie. I need to find the upper and lower values of my signals according to confidence interval and then show them on a graph...
  2. K

    (A Possible) Pooled P-Test Problem

    Historical data shows that 4% of the components produced at a certain manufacturing facility are defective. A particularly harsh labor dispute has recently been concluded, and management is curious about whether it will result in any change in this figure of 4%. A random sample of 500 items...
  3. K

    A simple confidence problem that I can't seem to solve

    Mr. Grumpy and Mr. Happy are both running for Governor. Mr. Grumpy will eventually win the election with 51 percent of the vote. A day before the election, a state-wide newspaper surveys 100 people about their choice for governor. Assume that survey respondents accurately report who they will...
  4. J

    Confidence Interval in Statistics test

    Hi all, I just had a test with the following question, of which I doubt the 'correct' answer: Taking a level of significance of 5% in a hypothesis test and not rejecting the null hypothesis, is the same as saying: A. We are 95% confident that the results have occurred by chance B. We are 95%...
  5. M

    Nonparametric data analysis

    I'm asking for advice. Topic of my research is brain iron accumulation. My task is the next . I have one dependent variable that is cathegorical and binominal(patient has the pathology or does not). And six independent variables that are continuous and nonpatametric. The question is :how can i...
  6. K

    Formula for the Confidence interval?

    Formula for the Confidence interval, assuming for a Sample whose standard deviation is same as Population. I need to know the exact formula. I need to know if there is any square root of n in the denominator. Anyone who knows the formula please share.
  7. A

    [AMOS] - interpretation of bootstrap indirect effects for one-tailed hypothesis

    Hello all, I'm testing for mediation using bootstrapping in AMOS. This method reports results for two-tailed significance, but my hypotheses are directional. With bootstrapping, significance is assessed based on confidence intervals - though a p-value is also provided. For regression, I would...
  8. A

    AMOS - interpretation of bootstrap indirect effects for one-tailed hypothesis

    Hello all, I'm testing for mediation using bootstrapping in AMOS. This method reports results for two-tailed significance, but my hypotheses are directional. With bootstrapping, significance is assessed based on confidence intervals - though a p-value is also provided. For regression, I would...
  9. D

    How do you create an acceptance criteria range for multiple populations?

    I am trying to create a quality control acceptance criteria range for my company's product. So here is an example of my problem: A car is traveling on a straight road and through scientific studies, I am able to predict the distance where the car will travel at a fixed time. From...
  10. Q

    P values from 95% CI using poisson distribution

    Hi, Hope I'm in the best place for an answer :) I have a study across 10 years. I have an incidence rate that was calculated for each year along with the 95% confidence interval using a Poisson distribution. My question is how do a get p-values for pairwise comparisons? I understand I can say...
  11. R

    Confusion between z and t values

    Hi, Alright so I have some confusion on when to use specific tests and the z vs t test. Given this example (not my homework) could someone please clarify. Alright say you have a random sample of size 200. You find the sample mean to be 10 and the sample standard deviation to be 5. What...
  12. J

    CI to percentage change in ICC

    I'm running fixed effects models to estimate changes in intra class correlations. I first run an unconditional model and then a second model including only level-2 factors. I'm interested in the reduction of the icc when adding only level-2 factors. I'm interested in expressing the...
  13. T

    Question about degrees of freedom in an independent sample t-test

    I've been asked the following question by a scientist who is not a statistician: Suppose we take a sample $x_1,…,x_n$ from a population that we can assume is normal (I don't think this assumption is critical). We then calculate the sample mean $\bar x¯$ and variance $s^2$. We then take a...
  14. E

    Overlapping confidence intervals

    Say I have a calculation model, calculating the a mean (lets say 36) value (with +-2 95% CI) as uncertainty for the calculation result. Then I measure the value 6 times, to a mean of 33 with (+1.5 95% CI), so the CI overlaps by .5 I want to say something about the compliance...
  15. 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...
  16. K

    Measuring the effect of in-store Promotions

    Hello, I am testing the effect of a new in-store promotion technique (treatment). It is applied during product promotions, as a compliment to regular promo displays, to further improve sales. I have the treatment in only one store but on several products promotions in that store (I have...
  17. A

    Help with figuring out confidence interval level

    Hello. My group was conducting a statistics study and we had all our data in an Excel file. We held a pretest (asked survey to nonmembers of the population but had the same characteristics). The results that we got from there was what helped us determine the needed sample size from the actual...
  18. M

    Confidence interval: true or false?

    We have measured the concentration cesium-137 in the tissue of 15 tunafish. We may consider the distribution as normal distribution and a 95 % Confidence Interval for the mean concentration was calculated to (5.03 to 6.71) (Bq/kg). Is the following statement true or false: "The interval means...
  19. R

    Exp(B) or CI values with the letter "E"

    Dear all, I am running a Multinomial Log. Regression. Everything seems fine but I do not understand when Exp(B) oder CI values are like 1,000E-013. I see this result although, the goodness of fit of the overall model is appropriate. For example in: B=-107,4, p=0,031 Exp(B)=1,000E-13...
  20. M

    Can you use the same data twice to construct a confidence interval?

    A while ago I was asked the following question: What is with a 95% probability the maximum number of defects, given a population of size N=800 of which we inspected n=100 and found k=0 defects. I constructed a confidence interval based on the assumption of a binomial distribution and gave...