Question

a scientific study looked at the effect of tanning beds on dna damage. the scientists took skin cells and exposed them to uv radiation (the type used in indoor tanning beds) for different lengths of time: some for 1 minute, some for 5 minutes, some for 15 minutes, and some for 30 minutes. they then looked for signs of dna damage and compared the results to cells that had never been exposed to uv light. what is the dependent variable in this experiment?
a the number of skin cells
b the type of light
c the length of time the cells are exposed to uv light
d the untreated cells
e the amount of dna damage in the cells

question 13
2.5 points
we have all heard that dietary fats are linked to higher incidences of heart disease and cancer in humans. choose the proper hypothesis that a scientist could test to examine this observation.
a eating more meat causes cancer.
b eating a diet of lard makes you fat.
c dietary fat, heart disease, and cancer are all somehow interrelated.
d fat levels above 30% of calories in the diet are correlated with an increase in heart disease.

Explanation:

First Question (Dependent Variable in Tanning Bed Experiment)

The dependent variable is what's measured in an experiment (depends on the independent variable). Here, the experiment tests how UV exposure time (independent) affects DNA damage. So the amount of DNA damage is what's measured. Option A: number of cells isn't the focus. Option B: type of light is fixed (UV). Option C: exposure time is independent. Option D: untreated cells are a control. Option E: DNA damage is the dependent variable.

A testable hypothesis should be specific. Option A: focuses on meat, not dietary fat broadly. Option B: focuses on weight, not disease. Option C: is vague (interrelated but not testable). Option D: specifies fat levels (above 30% of calories) and links to heart disease increase, which is testable.

Answer:

E. the amount of DNA damage in the cells

Second Question (Proper Hypothesis on Dietary Fats)