What exactly is a test statistic?When examining data samples, a test statistic quantifies the correctness of the expected data distribution in relation to the null hypothesis.
The statistic is determined by the type of data analysis method used and reflects how well your data fits the projected distribution for the given test.
Types of test statisticsThe following test statistics are some of the common applications data professionals use when performing statistical analysis:
T-value The t-value is one type of test statistic that results from performing either t-tests or regression tests. Evaluating the t-value requires testing a null hypothesis where the means of both test samples are equal. A t-value may be calculated using a typical t-test using the formula:t = (X - 0) / (s / n), where X is the sample mean, 0 is the population mean, s is the sample standard deviation, and n is the sample size.
Z-valueAnother typical test statistic where the null hypothesis says that the means of two populations are equal is the z-value. This statistic goes beyond the t-value, which only examines a subset of the population. You may use the following formula to calculate the z-value:z = (X - ) /, where X represents the raw data or score, is the population mean, and is the population standard deviation.