Standard Deviation and Mean. To compare the difference between two means, two averages, two proportions or two counted numbers. There are different equations that can be used to calculate confidence intervals depending on factors such as whether the standard deviation is known or smaller samples (n. 30) are involved, among others. Enter how many in the sample, the mean and standard deviation, choose a confidence level, and the calculation is done live. The formula to calculate the confidence interval is: Confidence ... where: p 1, p 2: sample 1 proportion, sample 2 proportion; z: the z-critical value based on the confidence level; n 1, n 2: sample 1 size, sample 2 size; To find a confidence interval for a difference between two population proportions, simply fill in the boxes below and then click the “Calculate” button. Confidence Interval Calculator. A number of additional statistics for comparing two groups are further presented. Two Independent Samples with data Calculator. Just enter the inputs of two samples in the above T statistic calculator for two Samples and click calculate to get the result. The confidence interval (also called margin of error) is the plus-or-minus figure usually reported in newspaper or television opinion poll results. Two-sample t-test free online statistical calculator. Confidence Interval for Two Independent Samples, Continuous Outcome There are many situations where it is of interest to compare two groups with respect to their mean scores on a continuous outcome. Including number needed to treat (NNT), confidence intervals, chi-square analysis. Read Confidence Intervals to learn more. For example, we might be interested in comparing mean systolic blood pressure in men and women, or perhaps compare body mass index (BMI) in smokers and non-smokers. This calculator uses JavaScript functions based on code developed by John C. Pezzullo. T-test online. Then enter the tail type and the confidence level and hit Calculate and the test statistic, t, the p-value, p, the confidence interval's lower … Type in the values from the two data sets separated by commas, for example, 2,4,5,8,11,2. The means are from two independent sample or from two groups in the same sample. Use the Standard Deviation Calculator to calculate your sample's standard deviation and mean. The above method calculates the difference between the observed means in two independent samples. Confidence interval for a proportion. This project was supported by the National Center for Advancing Translational Sciences, National Institutes of Health, through UCSF-CTSI Grant Numbers UL1 TR000004 and UL1 TR001872. Sample Size Calculator Terms: Confidence Interval & Confidence Level. A significance value (P-value) and 95% Confidence Interval (CI) of the difference is reported.