Question

A group of researchers have shown potential for dont-b-sad to alleviate the severity of depressive behaviors in rodents; now it’s time for clinical trials in humans. To do this, a sample of 300 individuals diagnosed with clinical depression in the state of Illinois were randomly assigned to one of three treatment groups: • 100 individuals received a daily dose (60 mg pill) of dont-b-sad. • 100 individuals received a sugar pill with no active ingredients. • 100 individuals received no intervention whatsoever (in fact, these individuals were un-medicated).

Importantly, the two pill groups were blind to (i.e., they did not know) whether or not they received the active or inactive pill. The severity of depression was quantified using the Beck’s Depression Inventory-II (BDI-II), a commonly used tool for assessing depression severity. Here are a few points regarding the BDI-II: • 21-item, self-report, multiple-choice inventory; takes about 10 minutes to complete. • Revision of the original BDI developed in 1996. • Widely used indicator of the severity of depression, which has a sensitivity rating of 81% and specificity rating of 92% (both are very good). • Available in multiple languages. • Monitors change in depression severity over time (it can be used repeatedly on the same individual – this is not always the case with psychological assessments).

Importantly (for this assignment), the BDI-II items are rated on a 4-point scale ranging from 0 to 3 based on severity of each item and the maximum total score is 63. The BDI produces a raw score, from 0-63. However, we can label the severity of their depression based on an individual’s raw score: • A raw score of 0-13 = minimal depression • A raw score of 14-19 = mild depression • A raw score of 20-28 = moderate depression • A raw score of 29-63 = severe depression

Please note that the BDI can produce a raw score (0-63) or a label (minimally, mildly, moderately, or severely depressed).

This clinical trial began by administering all 300 individuals the BDI-II. This initial BDI-II assessment (before any pills were given) showed that all 300 individuals fell in the range of raw scores that indicate severe depression (29-63). Then 100 individuals took dont-b-sad for 90 days, 100 individuals took the sugar pill for 90 days, and 100 individuals went un-medicated for 90 days. On the 91st day all individuals completed the BDI-II again (“follow-up”) to assess any changes in depression severity. Here are the results: • Of the 100 individuals that received dont-b-sad, 60 of them scored in a range that indicated severe depression at follow-up, 37 of them scored in a range that indicated moderate depression, and 3 of them scored in a range that indicated mild depression. • Of the 100 individuals that received the inactive sugar pill, 96 of them scored in a range that indicated severe depression at follow-up, while 4 of them scored in a range that indicated moderate depression. • Of the 100 individuals that received no intervention (un-medicated), 99 of them scored in a range that indicated severe depression at follow-up; one individual did not return to complete the study.

Now, with all of the above information, answer the following questions

1) Is this a correlational or experimental study? Why?

2) What is the independent variable in this study? How many levels, or conditions, are there, and what are they?

3) Is the independent variable a true or quasi-independent variable? Why?

4) What is the dependent variable in this study?

5) What type of measurement scale (nominal, ordinal, interval, or ratio) is the BDI-II? Why (note: there is one “correct” answer, but one could argue for an alternative answer. Thus, the justification for your answer is very important)?

Answer 1

A group of researchers have shown potential for dont-b-sad to alleviate the severity of depressive behaviors in rodents; now it’s time for clinical trials in humans. To do this, a sample of 300 individuals diagnosed with clinical depression in the state of Illinois were randomly assigned to one of three treatment groups: • 100 individuals received a daily dose (60 mg pill) of dont-b-sad. • 100 individuals received a sugar pill with no active ingredients. • 100 individuals received no intervention whatsoever (in fact, these individuals were un-medicated).

Importantly, the two pill groups were blind to (i.e., they did not know) whether or not they received the active or inactive pill. The severity of depression was quantified using the Beck’s Depression Inventory-II (BDI-II), a commonly used tool for assessing depression severity. Here are a few points regarding the BDI-II: • 21-item, self-report, multiple-choice inventory; takes about 10 minutes to complete. • Revision of the original BDI developed in 1996. • Widely used indicator of the severity of depression, which has a sensitivity rating of 81% and specificity rating of 92% (both are very good). • Available in multiple languages. • Monitors change in depression severity over time (it can be used repeatedly on the same individual – this is not always the case with psychological assessments).

Importantly (for this assignment), the BDI-II items are rated on a 4-point scale ranging from 0 to 3 based on severity of each item and the maximum total score is 63. The BDI produces a raw score, from 0-63. However, we can label the severity of their depression based on an individual’s raw score: • A raw score of 0-13 = minimal depression • A raw score of 14-19 = mild depression • A raw score of 20-28 = moderate depression • A raw score of 29-63 = severe depression

Please note that the BDI can produce a raw score (0-63) or a label (minimally, mildly, moderately, or severely depressed).

This clinical trial began by administering all 300 individuals the BDI-II. This initial BDI-II assessment (before any pills were given) showed that all 300 individuals fell in the range of raw scores that indicate severe depression (29-63). Then 100 individuals took dont-b-sad for 90 days, 100 individuals took the sugar pill for 90 days, and 100 individuals went un-medicated for 90 days. On the 91st day all individuals completed the BDI-II again (“follow-up”) to assess any changes in depression severity. Here are the results: • Of the 100 individuals that received dont-b-sad, 60 of them scored in a range that indicated severe depression at follow-up, 37 of them scored in a range that indicated moderate depression, and 3 of them scored in a range that indicated mild depression. • Of the 100 individuals that received the inactive sugar pill, 96 of them scored in a range that indicated severe depression at follow-up, while 4 of them scored in a range that indicated moderate depression. • Of the 100 individuals that received no intervention (un-medicated), 99 of them scored in a range that indicated severe depression at follow-up; one individual did not return to complete the study.

Now, with all of the above information, answer the following questions

1).Is this a correlational or experimental study? Why?

This is experimental study because there is intervention in the study. (200 individuals received treatment).

2) What is the independent variable in this study? How many levels, or conditions, are there, and what are they?

Type of treatment is the independent variable. There are 3 levels. They are 60 mg pill , sugar pill and no treatment.

3) Is the independent variable a true or quasi-independent variable? Why?

The independent variable a true independent variable because the subjects were randomly assigned to one of three treatment groups.

4) What is the dependent variable in this study?

Dependent variable is severity of depression.

5) What type of measurement scale (nominal, ordinal, interval, or ratio) is the BDI-II? Why (note: there is one “correct” answer, but one could argue for an alternative answer. Thus, the justification for your answer is very important)?

Severity of depression is in ratio scale.

There are 21 items in the scale and each item is scored 0 to 3. The total score range from 0 to 63. There fore there is true 0 value in the data. Therefore it is a ratio scale.