T-tests
T-tests T-tests The Good News About T-tests We’ve arrived! Sort of! You’ve learned how to describe your data with measures of central tendency and dispersion (after you’ve determined the appropriate level of measurement), you’ve learned about probability and why we care about normal distributions and how we can know that the mean of any sample distribution is likely pretty close (within 1 standard deviation) of the population mean. You’ve also learned how to tell if a sample mean differs significantly from a population mean if we have the population mean and standard deviation. With these tools, you can already answer some interesting questions! But, many of our questions are not about differences between a sample and the population, but differences between groups . I think of criminals and non-criminals, men and women, people with certain risk levels or number of victimizations or a pre-test-post-test experiment...