One Sample T-tests

1. One Sample T-tests • One sample t-tests are used in the following two situations • The size of a sample is less than 25 • The population standard deviation is unknown • The formula for a one sample test uses the estimated population standard deviation to calculate the standard error

2. Estimated Standard Error • The estimated standard error uses the estimated population standard deviation • This formula has a correction factor in the denominator of -1

3. Region of Rejection and Retention • Determining whether or not to reject the null depends on where the obtained t value falls within the t-distribution • A t score that is close to 0 will likely be in the region of retention • A t score that is far from 0 will likely be in the region of rejection

4. Directional Tests • One tailed tests place the entire region of rejection in a single tail • Two tailed tests divide the region of rejection into portions for each tail

5. t-Distributions • The shape of the t-distribution changes depending upon the size of your sample