Identify whether the texts in bold are discrete or continuous variables:

Question

It has been hypothesized that vitamin D is associated with androgen levels in men. We,

therefore, aimed to evaluate whether vitamin D supplementation increases serum total

testosterone (TT) levels in men with low TT levels at baseline. Methods: The Graz Vitamin

D&TT-RCT is a single-center, double-blind, randomized placebo-controlled trial conducted

between March 2013 and November 2017 at the endocrine outpatient clinic at the Medical

University of Graz, Austria. One-hundred healthy men with serum TT levels < 10.4 nmol/l and

25-hydroxyvitamin D [25(OH)D] levels < 75 nmol/l participated in the trial. Subjects were

randomized to receive 20,000 IU of vitamin D3/week (n = 50) or placebo (n = 50) for 12 weeks.

Primary outcome was TT measured using mass spectrometry. Secondary outcomes were free

testosterone, free androgen index, sex hormone-binding globulin, estradiol, follicle-stimulating

hormone, luteinizing hormone, metabolic characteristics, and body composition. Results:

Ninety-four men [mean age and 25(OH)D: 47 (± 12) years and 56.3 (± 18.3) nmol/l, respectively]

completed the study. We found no significant treatment effect on serum TT or on the remaining

secondary outcome variables. Conclusion: Vitamin D treatment had no effect on serum TT

levels in middle-aged healthy men with low TT levels.

Independent variable:

Dependent variable __________________________________

List a maximum of 3:

A. Nominal variable: ________________________________________

B. Ordinal: ________________________________________

C. Interval: ________________________________________

D. Ratio: ________________________________________

Answer 1

Independent variables are variables you control for from the start of the experiment, it was the administering of either a placebo or 20,000 IU of vitamin D3/week. This is also an example of a nominal variable, as it can be split into distinct categories.

"outcome" is a key term that suggests you are looking at an dependent variable, in this case, Total testosterone (TT) levels. This is also an example of a Ratio, as it is a numeral variable that includes a true zero.

For a third variable, I would probably list metabolic characteristics as a second nominal variable.