PSYCH 2220 Chapter Notes - Chapter 9: Confidence Interval, Test Statistic, Squared Deviations From The Mean
2 Mar 2018
School
Department
Course
Professor
Document Summary
The t test tells us how confident we can be that the sample differs from the larger population. As sample size increases, the t distribution more resembles the z distribution. Use them when you don"t know 1) the pop. st dev and 2) you can compare 2 samples. There is 1 t distribution for every sample size. Smaller sample size = flatter/more spread out t distributions. Any sample is likely to have less spread than the entire pop. Divide by (n - 1) to get the mean of the squared deviations. We subtract 1 from the sample size in the denominator to correct for the probability that the sample st dev slightly underestimates the actual st dev in the pop. Use lowercase s bc it is a statistic and not a parameter. Step 2) use the sample mean in the corrected formula for the st dev.
