Using statistics to compare instructional programs. Before beginning a unit on frog anatomy. a seventhgrade biology teacher gives each of the 24 students in the class a pretest to assess their knowledge of frog anatomy. The teacher wants to compare the effectiveness ofan instructional program in which students physically dissect frogs with the effectiveness ot'a different program in which students use computer software that simulates the dissection ofa frog. After completing one ofthe two programs, students will be given a posttest to assess their knowledge of frog anatomy. The teacher will then analyze the changes in the test scores {their score on the posttest minus their score on the pretest]. Suppose the teacher decides to allow the students to select which instructional program on t'rog anatomy (physical dissection or computer simulation} they prefer to take. Furthermore, suppose that I l snidents choose actual dissection and 13 students choose computer simulation. Here are the results in a test of signicance to compare the two groups: Computer Slmulatlon Group Actual Frog Ills-section Group Preteet Postteet Difference {posttest-pretest) Protest Posttest Dill'erenoe [posttest-pretest] 1 5-8- as at] 1 as 96 1t] 2 43 re 30 2 TB 36 B 3 59 as at] 3 as 99 1t] 4 55 35 30 4 a5 93 B 5 54 34 30 5 a4 9-1 19 E BI) 90 30 6 90 9a 3 7 43 re 30 7 TB as 1D 3 53 33 30 a a3 91 B Q 4? i"? 30 s I? a? 1D 10 56 as 30 1D as 9-1 B 11 55 35 30 11 a5 95 1D 12 H as 11 13 ?5 a? 12 Mean g_1 St Dev 1.04 Mean 2?.2 St Dev 6.95 The teacher uses a two sample signicance test of means to make a comparison between the two groups. She tests the hypothesis that students who use the computer simulation will see a greater improvement in their scores. I. Null & Alternate Hypothesis :1. H\": p. = u: 1.. Ha: Ill 1* 112 Step 2: 2. Test Statistic: t = 9.2? 3. pvalue = {1.000 4. Reject Hp. Evidence shows that students who use the computer simulation will see a greater improvement in their scores. In tact. since the pvalue is 0. there is strong evidence that this is the case