Experimental Design Experimental Designs An Overview

Basic Experimental Designs t test for independent samples Completely Randomized Design Experimental design model equation t test for dependent samples Randomized Block Design Experimental design model equation The F-Ratio

Basic Factorial Designs Completely Randomized Factorial Experimental design model equation Randomized Block Factorial Experimental design model equation Split Plot Factorial Interactions

Selecting an Appropriate Design 1. Does the design permit the calculation of a valid estimate of the experimental effects and the error effects? 2. Does the data-collection procedure produce reliable results? 3. Does the design possess sufficient power to permit an adequate test of the statistical hypotheses?

Selecting an Appropriate Design 4. Does the design provide maximum efficiency within the constraints imposed by the experimental situation? 5. Does the experimental procedure conform to accepted practices and procedures used in the research area? Other things being equal, a researcher should use procedures that offer an opportunity for comparing the findings with the results of other investigations.

Review of Statistical Inference Scientific hypothesis Statistical inference Statistical hypothesis Null hypothesis Alternative hypothesis Hypothesis testing

Sampling Distributions The distribution of a sample statistic that gives the probability associated with each value of the statistic over all possible samples of the same size that could be drawn from the population.

Central Limit Theorem States the characteristics of the sampling distribution of the mean One of the most important theorems in statistics Demo

Test Statistics Sample statistics – used to describe characteristics of samples or to estimate population parameters Test statistics – used to test hypotheses about population parameters z scores t score degrees of freedom

Hypothesis Testing Type I Errors Type II Errors Power Correct acceptance One-tailed & two-tailed tests and power Determining sample size Practical significance