Select the correct statement regarding experiments.

• A researcher can carefully control the explanatory variables and observe human responses.
• A researcher can ignore explanatory variables and observe human responses.
• A researcher can carefully control the explanatory variables but not observe human responses.
• A researcher can observe the explanatory variables but not control human responses.

Maria flipped a coin 60 times, and the coin came up tails 32 times.

What is the relative frequency of the coin turning upheadsin this experiment?Answer choices are rounded to the hundredths place.

• 1.88
• 0.47
• 0.53
• 2.14

A sports trainer is going to do experiment on the effect of Vitamin D supplements and his athletes.He randomly assigns all of his patients to either take Vitamin D supplements or take a placebo.

What type of experimental design does this situation illustrate?

• Randomized Block
• Matched-Pair
• Simple Random
• Completely Randomized