Confidence interval Definition and 86 Threads

Homework Statement I have 20 data points of the surface roughness of oil pipes, the mean, and the std of the sample. I need to get a 95% confidence interval of the mean surface roughness of these pipes. I did a boxplot, and found that it's negatively skewed, and therefore not normally...

Hello, Let me get right to my problem. I have an experimental distribution and a single-parameter theoretical distribution. I want to find the value for the best fit theoretical distribution that agrees with my experimental data for the bulk of the distributions (the tails of my...

Homework Statement (I translated this from french) Some n dice are thrown and the sum of all their face values is 117. Estimate n through a confidence interval of 90%. In other words, of all the possible rolls of n dice that sum up to 117, find a range in which n should be located 90%...

Homework Statement In a primary school, the mean height of the students of primary 1 students is 120cm. Given a sample size of 40, the confidence interval is 117 and 123. Find the confidence interval if the sample size is 30 instead. Homework Equations Standard deviation and confidence level...

Homework Statement X1,...Xn is a random sample from N(μ, σ^2) Homework Equations Estimator of μ maybe? a1 + a2 = a a1 = a2 = a/2 (x-μ)/(σ/√n)~N(0,1) ((x-μ)/σ)^2~Chi square(1) The Attempt at a Solution I tried to replace μ with its estimator xbar but that gives me 0.

Homework Statement Homework Equations The Attempt at a Solution

The following are summary statistics for a data set. Would it be appropriate to use the Student's t- distribution to construct a confidence interval for these data? Explain clearly! Sample size = 10 Mean = 8.905 Median = 6.105 Standard deviation = 9.690 Minimum = 0.512 Maximum = 39.920...

The following are summary statistics for a data set. Would it be appropriate to use the Student's t- distribution to construct a confidence interval for these data? Explain clearly! Sample size = 10 Mean = 8.905 Median = 6.105 Standard deviation = 9.690 Minimum = 0.512 Maximum = 39.920...

Say that there is a random variable X ~ U(a,b) where U is the discrete uniform distribution on integers on the interval [a,b]. Sample n such variables with the same (unknown) parameters a and b. Using those samples it's possible to estimate the mean either by taking the sample mean (sum the...

Hello, I'm doing some nonlinear regression fitting, and I have a set of data with n data points and I am fitting the data to a model which contains 3 parameters. I can get a confidence interval from the program I'm using for each parameter, but how can I calculate the standard deviation for...

Homework Statement Janet sells cookware at home parties, she wants to estimate the average amount a client spends at each party. A random sample of 35 receipts gave a mean of X bar = $34.70 with standard deviation s = %4.85. a) find a 90% confidence interval for the average amount spent by...

Homework Statement Let X1, X2,...Xn be a random sample from the distribution with probability density function fX (x;θ) = (θ+1)(1-x)θ, 0<x<1 θ>-1 a) What is the probability distribution of Y= -\sum ln(1-Xi from i=1 -> n b) Suggest a (1-α)100% confidence interval for θ based on Y=...

From Koosis, I pieced together the following algorithm. Is sigma known? Yes? Then calculate the exact confidence interval using a normal distribution to estimate that of the sample means, with mean = the mean of sample means = the mean of the population, \mu_{\overline{x}}=\mu, and...

My course notes and textbook express this differently: To construct the confidence interval for diff. between means, Course notes (\bar{x1} - \bar{x2})\pmE Textbook (\bar{x1} - \bar{x2}) - E < \mu1 - \mu2 < (\bar{x1} - \bar{x2}) + E why the difference?

I am trying to calculate the confidence interval for this problem using my T-84, and it's driving me mad because I'm so close to the correct answer. The problem is Homework Statement The answer to this problem is (22769.83, 30059.41) (This is an example problem.) When I try to duplicate...

So as the title says. How do you calculate the confidence interval that is not on the t-table. For example how do you calculate the confidence interval for 97%? Assume that it is a normal distribution, you are not given σ and that n<30. Is there a formula? Or should i look for a more specific...

I got a question which has been confused me for a long time. The question is to calculate the 95% confidence interval for a curve. I have already learned how to calculate for a straight line. For example, the cumulative distribution function (CDF) could be expressed as below: Y = 1/2 * {1...

when we calculate a value, say @95% we get 9.99+- .002 this value is describing a parameter of the true population right? it is not saying 95% of the time we get samples, it will fall in this range correct? We never infer anything about statistics, only parameters of populations right...

How would you go about finding the confidence interval for the parameters of the gamma distribution? I have had a look online and haven't found anything with the answer... Thanks

Homework Statement What formula do I need to find the confidence interval, when I have got: - Number of samples - Level of Confidence - The assumed (1st guess) accuracy Homework Equations I found the following equation online: µ = z * [p * (1 - p) / n] ^ (-1/2) The Attempt at...

A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus Yellow Pages. On each page, the mean area devoted to display ads was measured(a display ad is a large block of multicolored illustrations, maps, and text). The data (in square...

I don't know which forum to put this in... So here goes. Homework Statement Basically, I have gathered 30 data points that vary from about 1.3 - 4.7 in value (it doesn't matter what it is) with a mean of 2.98. Since I haven't done any statistics courses yet, I used the built in Excel...

How would you find CI for some function of a parameter? the case I'm particularly interested in is an approximate CI for p^2 where p is the proportion in the binomial model. http://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval

Hi, if I have the confidence interval for the point estimate of an option price A which was found through simulation, can I also find a confidence interval for delta (dA/dS), where S is underlying asset price, without further simulation? thanks, sl

Homework Statement http://www.geocities.com/asdfasdf23135/stat15.JPG I am OK with part a, but I am having some troubles with part b. Homework Equations Width of a Confidence Interval The Attempt at a Solution Attempt for part b: http://www.geocities.com/asdfasdf23135/stat16.JPG...

The following distinguishes TWO cases for large samples confidence interval for difference in means: http://www.geocities.com/asdfasdf23135/stat11.JPG where Sp^2 is the pooled estimate of the common variance, n1 is the sample size from the first population, n2 is the sample size from the...

Let's say we know this: \sqrt{n}\left(\widehat{\theta} - \theta\right) \sim \mathcal{N}\left(0, \frac{1}{F(\theta)}\right) How do we get from this information to this expression of confidence interval for \theta? \left( \widehat{\theta} \pm...

I am trying to calculate the chi squared function for life data and a confidence level of 95%. I have 10 data points, a specified confidence level (95%), and 1 degree of freedom. I also have the alpha and beta parameters. Based on this information how can i calculate the chi squared statistic? I...

What's the probability that a confidence interval (with alpha=10%), will have at least 85 of 100 predicted means within the calculated interval range (xbar +/- 1.645(sigma/sqrt(n)))? I understand that on average 90% of my means will be located in this range (and I know how to find this...

Lets say you have 5 trials, and 5 output let's say {5, 43, 60, 30 , 4}...so how would u get the chi sqaure from here & the confidence interval. i haven't work on prob &statc in years, thanks a lot for help folks

Lets say you have 5 trials, and 5 output let's say {5, 43, 60, 30 , 4}...so how would u get the chi sqaure from here & the confidence interval. i haven't work on prob &statc in years, thanks a lot for help folks

A container of oil is supposed to contain 1000 ml of oil. We want to be sure that the standard deviation of the oil container is less than 20 ml. We randomly select 10 cans of oil with a mean of 997 ml and a standard deviation of 32 ml. Using these sample construct a 95% confidence interval...

[Solved]Is a stats question,just need some clarity on it-"total width of less than 2. Homework Statement Hi.The result of a memory test is known to be normally distributed with mean mew and standard deviation 1.0. It's required to have a 95% confidence interval for mew with a total width of...

Hi, I am an 3rd engineering student working on my coop report. My job was to design routes for survey work, and come up with figures of potential time savings if this was to be done on a grand scale. The sites are divided into 15 regions (by geography) but are not in any particular order...

What is the 95% confidence interval for 100 ohm resister with 10% tolerence? Here is my work so far, can someone please tell me if I am doing it wrong or right? Thank you in advance. from table 95%: k = 1.96 100 * 0.1( which is the 10% tolerance) = 10 10 / sigma >= 1.96 Sigma <=...

I*m looking for some help with a statistics question: Builder A and Builder B both take random samples of nails, and the width of the nails are measured in centimetres - Builder A estimates that a 95% confidence interval for the width of the nails is 1.2 +/- 1.96 * 0.05. Builder B estimates...