PS 601 Notes – Part II Statistical Tests. Notes Version - March 8, 2005. Statistical tests. We can use the properties of probability density functions to make probability statements about the likelihood of events occurring.
PowerPoint Slideshow about 'PS 601 Notes – Part II Statistical Tests' - daxia
Download NowAn Image/Link below is provided (as is) to download presentation
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
When we cannot use the population standard deviation, we must employ a different statistical test
Think of it this way:
The sample standard deviation is biased a little low, but we know that as the sample size gets larger, it becomes closer to the true value.
As a result, we need a sampling distribution that makes small sample estimates conservative, but gets closer to the normal distribution as the sample size gets larger, and the sample standard deviation more closely resembles the population standard deviation.
The t-test formula gives you a value that you can compare to the critical value.
Conducting a one-tailed test, if the calculated t-value is greater that the critical value of t, or less than –(critical value of t), we conclude that the sample is significantly different that the population.
Choice of t or –t is determined by the one-tailed test direction.
Note that a t-value that exceeds the critical value means that the probability of that t is less than the selected α-level.