CJUS K300 1nd Edition Lecture 12 Outline of Last Lecture I Hypothesis testing 2 tailed non directional tests Outline of Current Lecture II Hypothesis testing 1 tailed directional tests Current Lecture Why Reasons to specify a directional hypothesis 1 It fits the theory 2 It gives a mathematical advantage In a two tailed test both the tails or extremities are included 2 5 in each tail For a one tailed test we combine the tails making it 5 in one of the tails How do we know which tail to use As a good rule of thumb you can follow the sign of the null hypothesis Means right hand tail Means left hand tail usually Steps in testing a null hypothesis with a 1 tailed test so similar to the 2 tailed test 1 State your null research hypotheses 2 Decide on your alpha level usually given to you 3 Look up the critical value Zcrit and draw a graph if you wish x Z obt s 4 Calculate n 5 Compare Zobt and Zcrit 6 State your conclusion in words Using the same example from last class with 2 tailed tests we will look again at the Violence Attitude Scale Possible range 1 50 higher score taking domestic violence more seriously Population of police officers 20 Sample of 75 officers x 20 8 s 4 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute H o 20 H 1 20 H 1 interpreted The sample of officers who have been through the 2 day training program come from a population of officers whose mean score on the Domestic Violence Attitude Scales is GREATER than 20 Alpha 05 corresponds to 1 65 Zobt 1 74 Reject the null Another example Do teenage shoplifters steal less valuable items than the general population of shoplifters You can find hints in the research question about the direction of the test Population of all shoplifters the mean value of stolen items 83 so 83 For a sample of 97 shoplifters ages 13 17 years the mean value of stolen items was 81 so X 81 s 11 alpha 05 look up alpha in the 1 tailed test column 1 65 Zobt 1 80
View Full Document
Unlocking...