Table 1.
Theoretical concepts, measurement items and item-statistics for the benefit scale
| Items | Concepts and Questions | Mean (SD) | Agree / strongly agree (%) |
IRT p-value# |
|---|---|---|---|---|
| * | Physical and Psychological benefits | |||
| Benefit4 | I am treated like a person and not a number by my research team | 4.43 (0.72) | 90.8% | <.001 |
| Benefit13 | It gives me a sense of hope about my cancer | 4.20 (0.74) | 87.2% | <.001 |
| Benefit18 | It is a way for me to actively treat the cancer | 4.13 (0.93) | 81.5% | <.001 |
| Benefit14 | I am hoping for a cure | 4.17 (0.99) | 78.9% | 0.001 |
| Benefit12 | I am able to extend my life | 4.02 (0.90) | 76.1% | <.001 |
| Benefit21 | I trust my researcher knows what is best for me | 4.07 (0.88) | 73.1% | <.001 |
| Benefit16 | I have access to drugs and other medicine/tests that are not available to me otherwise | 3.90 (1.14) | 71.3% | 0.001 |
| Benefit3 | My cancer is watched more closely than it would otherwise be | 3.93 (1.05) | 68.8% | <.001 |
| Benefit10 | I feel more informed about my specific type of cancer and the treatments | 3.72 (1.06) | 64.2% | <.001 |
| Benefit9 | It gives me information about my disease that it would not otherwise have | 3.60 (1.12) | 56.9% | <.001 |
| Benefit11 | It helps me know what to expect about my specific type of cancer | 3.58 (1.09) | 56.9% | <.001 |
| Benefit7 | It allows me to have some control over my cancer | 3.42 (1.19) | 54.6% | <.001 |
| Benefit6 | It lessens my stress associated with my cancer | 1.28 (1.24) | 47.2% | <.001 |
| Benefit5 | I worry less about my cancer when I participate in research | 3.25 (1.24) | 44.4% | <.001 |
| Benefit20 | It may reduce my risk of cancer in the future | 3.25 (1.17) | 40.7% | <.001 |
| Social and Economic Benefits | ||||
| Benefit2 | I might help future patients with my cancer (even though my participation might not help me) | 4.51 (0.60), 3–5 | 94.5% | 0.023 |
| Benefit1 | I am providing a valuable contribution to society | 4.38 (0.67) | 94.4% | 0.003 |
| Benefit8 | It may help my children or other family members in the future | 4.10 (0.98) | 76.1% | <.001 |
| Benefit19 | It does not interfere with my other life responsibilities | 3.66 (1.16) | 63.3% | 0.001 |
| Benefit15 | It helps me pay for the costs of drugs, medications, and/or tests that I might not otherwise been able to afford | 3.25 (1.28) | 43.1% | <.001 |
| Benefit17 | My insurance will likely cover all of my research expenses | 3.15 (1.13) | 38.0% | 0.002 |
| Benefit22 | I receive money for participating in the clinical trial | 1.94 (1.19) | 11.2% | 0.719 |
| Total | Scale Mean Score | 3.73 (0.58), 2.09–4.82 | ||
*
The number is the sequential order of the item in the actual scale.
#
p-value from IRT graded response model discrimination.
Items were measured on a Likert scale from 1 (Strongly Disagree) to 5 (Strongly Agree)
Alpha=0.895 for the total scale (number of items=22)
The mean scale score is normally distributed (skewness=−0.19, SE=0.23; Kurtosis=−0.22, SE=0.46)