Question

what null hypothesis is tested by an independent measures t-test? what value does the t-test compare?

Answer 1

The Independent samples t-Test compares means of two independent groups in order to determine whether there is statistical evidence that the associated population means are significantly different. The Independent Samples t-Test is a parametric test, which is also called Independent t-Test. When you perform a t-test, you're usually trying to find evidence of a significant difference between population means or between the population mean and a hypothesized value (1-sample t). The t-value measures the size of the difference relative to the variation in your sample data.