EDUR 8131

Correlated Samples t-test Exercise

Instructions

Present results using the table format presented in the notes entitled "Reporting Statistical Outcomes." Do not include SPSS output or hand-worked calculations; present only result tables and written comments on results.

1. Suppose you are a researcher interested in the factors influencing paper grading by professors. You have a hunch (and/or previous research) might lead you to predict that papers that are typed are rated higher than papers that are handwritten. So you have 10 freshman students currently taking English as well as an introductory psychology course each write one paper. They should each provide two copies of their paper (one typed and one handwritten). Next, we enlist the aid of 20 English instructors. We randomly assign 10 instructors to each of two groups. Each instructor in one group (the control group) will grade each of the 10 papers that are hand written, while the second group (the experimental group) will grade the same papers that are typed. Does typing a paper influence the grade it receives?

 Student Written Typed a 81 84 b 81 89 c 79 89 d 80 81 e 84 87 f 87 82 g 75 87 h 83 85 i 88 89 j 79 83

2. Investigators propose that students have elevated blood pressure during finals week due to stress and anxiety associated with testing. To assess this hypothesis, eight students volunteered to have their blood pressure taken at the beginning of the semester and then again during finals week. The blood pressure data (diastolic) is listed below. Is there any evidence that blood pressure levels do differ during finals week?

Table: Blood pressure data

 Student Week 1 Finals Week Rod 89 92 William 76 78 Barbara 84 92 Marvin 89 94 Dennis 74 93 Karen 66 74 Mora 56 65 Michael 74 73

3. A study was conducted to investigate the effectiveness of hypnotism in reducing pain. Results for randomly selected subjects are given below. At the 5% level of significance, test the claim that the sensory measurements are different for each student before and after hypnotism (scores are on a pain scale with higher scores indicating more pain). Assume sensory measurements are normally distributed.

Table: Pain

 Before 6.6 6.5 9 10.3 11.3 8.1 6.3 11.6 After 6.8 2.4 7.4 8.5 8.1 6.1 3.4 2