Psychology 202a Advanced Psychological Statistics September 28, 2017

The Plan for Today The Z test Assumptions The two-sample Z test The t test

Using the central limit theorem for inference The one-sample Z test Hypothesis testing steps Example: alpha=.05, two-tailed test

Using the central limit theorem for inference s = 10, n = 25, M = 105 Two ways to make a decision: critical value or exact p-value Demonstration in R

Assumptions of the Z test Independent observations. s is known. Distribution is normal or sample is sufficiently large. Problem: those assumptions are virtually never actually met.

The one-sample t test Solution to not knowing s : substitute an estimate of the standard deviation. Class example. The t test in SAS.