Inter item reliability with surveys

Inter item reliability with surveys

1. Inter-item Reliability 1

2. Inter-item Reliability With inter-item reliability or consistency we are trying to determine the degree to which responses to the items follow consistent patterns. 2

3. For example Let’s imagine that two items are designed to assess how “teachable” someone is. Item 1 is a difficult item for someone to agree with. So on a scale of 1 – 5 with 1 being “Strongly Disagree” and 5 being “Strongly Agree” here is what the response pattern might look like: 3

4. For example Let’s imagine that two items are designed to assess how “teachable” someone is. Item 1 is a difficult item for someone to agree with. So on a scale of 1 – 5 with 1 being “Strongly Disagree” and 5 being “Strongly Agree” here is what the response pattern might look like: 4 Respondent Item 1 Bob 1 Carla 2 Don 1 Elsa 3 Fiona 1 Gordon 2 Etc.

5. For example Now take a look at item 2. It is much easier to agree with: 5 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Fiona 1 4 Gordon 2 5 Etc.

6. For example 6 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Fiona 1 4 Gordon 2 5 Etc. Notice the consistency in the item response patterns

7. For example 7 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Fiona 1 4 Gordon 2 5 Etc. Bob & Fiona are less likely to agree with these items targeting teachableness .

8. For example 8 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Fiona 1 4 Gordon 2 5 Etc. But even though they are both less likely to agree they consistently agree more with item 2 than 1.

9. For example 9 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Fiona 1 4 Gordon 2 5 Etc. This shows a consistent pattern across items.

10. For example 10 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Bob 1 4 Gordon 2 5 Etc. Notice that this pattern holds across all of the other respondents. Item 2 is easier to agree with than Item 1

11. For example 11 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Bob 1 4 Gordon 2 5 Etc. Notice also that Elsa is the most agreeable across both items.

12. For example 12 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Bob 1 4 Gordon 2 5 Etc. And Bob & Fiona are consistently the least agreeable across both items.

13. For example 13 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Bob 1 4 Gordon 2 5 Etc. The item responses to this instrument, therefore, demonstrate high inter-item reliability or consistency across persons with different levels of the trait.

14. For example 14 Respondent Item 1 Item 2 Bob 1 4 Carla 2 5 Don 1 4 Elsa 3 6 Bob 1 4 Gordon 2 5 Etc. This type of reliability is measured principally by a statistic called Cronbach's Alpha and ranges traditionally from 0.00 (no consistency) to +1.00 (completely consistent).