If you instead know the population standard deviation, you should use our Confidence Interval Calculator for the Mean with known Population Standard Deviation. There are other confidence intervals you can use such as the confidence interval for the sample variance, the confidence interval for slope coefficients, or confidence intervals and prediction intervals for regression estimate . You take a random sample of 10 fingerlings and determine that the average length is 7.5 inches and the sample standard deviation is 2.3 inches. Instructions: This calculator computes a confidence interval for the population mean \(\mu\), in the case that the population standard deviation \(\sigma\) is not known, and we use instead the sample standard deviation \(s\). For an approximately normal data set, the values within one standard deviation of the mean account for about 68% of the set; while within two standard deviations account for about 95%; and within three standard deviations account for about 99.7%.Shown percentages are rounded theoretical probabilities intended only to approximate the empirical data derived from a normal population. This calculator finds a confidence interval for a population standard deviation, based on input provided by the user. Confidence interval of a sample without standard deviation. Learn more about population standard deviation, or explore other statistical calculators, as well as hundreds of other calculators addressing math, finance, health, fitness, and more. Or you may have happened to obtain data that are far more scattered than the overall population, making the SD high.If you assume that your data are randomly sampled from a population that follows a Gaussian distribution, This calculator can compute a 95% confidence interval for the standard deviation. Use this Confidence Interval Between Mean Calculator to find the mean, standard deviation, variance, number of datas, lower limit and upper limit of two data sets. ... finding z value for confidence interval without standard deviation. For the purposes of this calculator, it is assumed that the population standard deviation is known or sample size is larger enough therefore the population standard deviation and sample standard deviation is similar. Depending on which standard deviation is known, the equation used to calculate the confidence interval differs. The Calculation. Caution : you should really use the standard deviation of the entire population ! That's all I get from the text. Ask Question ... 3$ And the necessary quantile is $2.36$. 1. Please enter your data into the fields below, select a confidence level (the calculator defaults to 95%), and then hit Calculate. In case the population standard deviation is known, you can use this confidence interval calculator for a population means when the population standard deviation is known. But you can use the standard deviation of your sample if you have enough observations: at least n=30 , the more the better. I calculated the mean which is $15.53$ and the standard deviation which is $0.28$ but now I am stuck.