Experimental Study Methods PDF

Only way causation can be shown is with an experimental study in which an independent variable is manipulated to bring about an effect in the dependent variable (experimental study) Mediation Analyses - analytical approach \- can be employed when researchers are interested in testing a variable as...

Only way causation can be shown is with an experimental study in which an independent variable is manipulated to bring about an effect in the dependent variable (experimental study) Mediation Analyses - analytical approach \- can be employed when researchers are interested in testing a variable as a potential pathway between an independent and dependent variable \- correlation determines relationship between two variables prediction (regression) equation formula to predict some measure of performance based on the relationship between the predictor variables and the criterion \- the higher the relationship is between two variables the more accurately you can predict one from the other using correlation for prediction the higher the relationship is between two variables, the more accurately you can predict one from the other Testing differences between groups ex. training group A and B, randomly assigned groups. Only difference is the volume of intensity perfect correlation is 1.00 either +1.00 or -1.00 no relationship is 0.00 meaningfulness When you use statistics that test for differences between groups, you want to establish not only whether the groups are different, but also the strength the association between the independent and dependent variables. size of the difference between the two groups increasing statical power 1) Increase the difference between the means 2\) Decrease the variances for means of each group 3\) Increase sample size Why is obtaining power in research desirable? because the odds of rejecting the null hypothesis are increased repeated measures designs Repeated-measures designs identify and separate individual differences from the error term, increase power, require fewer participants, and study a phenomenon across time. carryover effect effect of being tested in one condition on participants\' behavior in later conditions (i.e., treatments given earlier influence treatments given later) \- can be problematic When would a researcher use an independent samples t test? A researcher would use and independent sample t test to determine whether two sample mean differ reliably from each other When would a researcher use a dependent samples t test? A dependent sample t test would be used t test the differences between the means of two sets of scores that are related in some manner Positive Pattern A, as you go up in one variable, you go up in another Negative pattern B, as you go down in one variable you go down in another Scattered Pattern C, no relationship Curvilinear Pattern D, no relationship but a relationship is being observed P value in fischerian frame work a continuous measure of compatibility between the observed data and the null hypothesis. power is the probability of rejecting the null hypothesis when the null hypothesis is indeed false (e.g., detecting a real difference), or the probability of making a correct decision. Importance of a control group based on Bishop and Thompsons textbook \"But in most situations where the aim is to test the effectiveness of an intervention for a particular condition, a study with a control group will be the best way to get useful information. Indeed, doing a study without controls is unethical if you end up investing the time of clients and professionals, and research funds, doing a study that cannot answer the question of whether the intervention is effective.\" Parametric statistical tests Applied to quantitative data, require assumptions about the distributional characteristics of data stratified sampling the population is divided on some characteristics before random selection of the sample convenience sampling involves selecting participants based on accessibility, due to their geological proximity advantages and disadvantages of convenience sampling - Advantage: provides quick people, inexpensive, uncomplicated method \- Disadvantage: low generalizability due to selection bias Show which image is the main effect of teaching environment verse main effect of motivational level - Main effect of teaching environment (right) \- Main effect of motivation level (left) \- Y-axis = Test Scores Red = High-Motivated Blue = Low-Motivated 1 = Traditional 2 = Interactive (no main effect when red and blue are parallel) effect size quantitative measure of the magnitude of the experimental effect Why is an effect size important Helps researchers understand the strength of a relationship and the differences of two variables. The larger the size the stronger the relationship mediator variable caused by the independent variable which influences the dependent variable. shows how or why an effect happens interaction effects The influence of one variable depends on the level of the other variable. What would a graph for interaction look like Non-parallel lines (crossing or diverging), indicating the relationship between the variables changes based on each other What would a graph for main effects look like Parallel lines, suggesting the variables affect the outcome independently of each other. main effects he independent influence of each variable on the dependent variable