l Identifying the appropriate Test Statistic Ask the following questions Are the data from measurements(continuous variables or counts(discrete variables)? Are the data from independent samples? Are the population variances approximately equal? Are the populations approximately normally distributed? What are the sample sizes? o 2002 The Wadsworth Group
Identifying the Appropriate Test Statistic Ask the following questions: • Are the data from measurements (continuous variables) or counts (discrete variables)? • Are the data from independent samples? • Are the population variances approximately equal? • Are the populations approximately normally distributed? • What are the sample sizes? © 2002 The Wadsworth Group
Ⅷ Test of(1-u2)a=a2 Populations normal Test statistic x1-x2)]-[1-1 hc24+)2+(2)2 and df=n,+n2-2 o 2002 The Wadsworth Group
Test of (µ1 – µ2 ), s1 = s2 , Populations Normal • Test Statistic and df = n1 + n2 – 2 –2 1 2 2 2 –1) 2 2 ( 1 –1) 1 ( where 2 2 1 1 2 1 0 ] 2 – 1 ] – [ 2 – 1 [ n n n s n s p s p n n s x x t + × + × = + = ÷÷ ÷ ÷ ÷ m m © 2002 The Wadsworth Group
I Example: Equal-Variances t-Test Problem 11.2: An educator is considering two different videotapes for use in a half-day session designed to introduce students to the basics of economics Students have been randomly assigned to two groups and they all take the same written examination after viewing the videotape. The scores are summarized below assuming normal populations with equal standard deviations, does it appear that the two videos could be equally effective? What is the most accurate statement that could be made about the value for the test? Videotape1:x1=77.1,s1=78,11=25 Videotape2:x=80.0,s2=8.1,m2=25 C 2002 The Wadsworth Group
Example: Equal-Variances t-Test • Problem 11.2: An educator is considering two different videotapes for use in a half-day session designed to introduce students to the basics of economics. Students have been randomly assigned to two groups, and they all take the same written examination after viewing the videotape. The scores are summarized below. Assuming normal populations with equal standard deviations, does it appear that the two videos could be equally effective? What is the most accurate statement that could be made about the p-value for the test? Videotape 1: = 77.1, s1 = 7.8, n1 = 25 Videotape 2: = 80.0, s2 = 8.1, n2 = 25 x 1 x 2 © 2002 The Wadsworth Group