Examples From: Psychology Business Engineering Biology
	Psychology Howell (1995) presents an example based on the research of Wegner, Compas, and Howell (1988) about the relationship between stress and mental health in first-year college students. Students completed a questionnaire about life events stress they had experienced and they also completed the Hopkins Symptom Checklist. High scores on Stress and Symptoms indicate high levels of life events stress and psychological problems, respectively. Below are the data for ten students selected from the larger study. Student 1 2 3 4 5 6 7 8 9 10 Stress 30 27 9 20 3 15 5 10 24 34 Symptoms 99 94 80 70 100 109 62 81 74 121 Does it appear that a student's score on Symptoms is related to his or her score on Stress? The graph to the right shows the student points divided into four sections by the means. Are there more students in the positive diagonal corners (upper-right and lower-left) or in the negative diagonal corners (upper-left and lower-right)? If there are more on the positive diagonal, this suggests there is a positive relationship between psychological stress and mental health symptoms. Return to Top Business Cryer and Miller (1994) on p. 178 present an example of two variables that might be related: a house's size, as measured in hundreds of square feet of living area, and its market value. Parcel 1 2 3 4 5 6 7 8 9 10 SqFt 5.44 6.94 7.67 8.25 8.99 9.65 10.33 10.60 11.06 12.98 MarketValue 25.2 37.4 33.6 38.0 37.6 37.2 40.4 44.8 42.8 45.2 Does it appear that a parcel's market value is related to its size in square feet? The graph to the right shows the points for each parcel divided into four sections by the means. Are there more parcels in the positive diagonal corners (upper-right and lower-left) or in the negative diagonal corners (upper-left and lower-right)? If there are more on the positive diagonal, this suggests there is a positive relationship between a parcel's size and its market value. Return to Top Engineering DeVore (1995) presents the following example on p. 475: The paper "A Study of Stainless Steel Stress-Corrosion Cracking by Potential Measurements" (Corrosion, 1962, pp. 425-432) reports on the relationship between applied stress (in kg/sq mm) and time to fracture (in hours) for 18-8 stainless steel under uni-axial tensile stress in a 40% CaCl2 solution at 100C. Ten different settings of applied stress were used, and the resulting data values (as read from a graph which appeared in the paper) were: Test 1 2 3 4 5 6 7 8 9 10 Stress 2.5 5 10 15 17.5 20 25 30 35 40 FailTime 63 58 55 61 62 37 38 45 46 19 Does it appear that the time for the steel to fail is related to the amount of stress applied? The graph to the right shows the points for each test divided into four sections by the means. Are there more tests in the positive diagonal corners (upper-right and lower-left) or in the negative diagonal corners (upper-left and lower-right)? If there are more on the negative diagonal, this suggests there is a negative relationship between stress and the time until failure. Return to Top Biology Ott (1993) presents this example on p. 452: Fifteen male volunteers ate a low-cholesterol diet for four weeks. Below are the ages and the reduction in cholesterol (in mg per 100 ml of blood serum) for each participant: Participant 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Age 45 43 46 49 50 37 34 30 31 26 22 58 60 52 27 Reduce 30 52 45 38 62 55 25 30 40 17 28 44 61 58 45 Does it appear that Age is related to the Reduce (the amount of cholsterol reduced by eating the diet)? The graph to the right shows the points for each dieter divided into four sections by the means. Are there more dieters in the positive diagonal corners (upper-right and lower-left) or in the negative diagonal corners (upper-left and lower-right)? If there are more on the positive diagonal, this suggests there is a positive relationship between age and the amount of cholesterol reduced. Return to Top