A medical team wants to determine which form of mastectomy is most effective for prolonging life for women with breast cancer: radical mastectomy (removal of breast, chest muscles, and lymph nodes), simple mastectomy (removal of the breast only), or "lump-ectomy" + chemotherapy (removal of only the cancerous lump, leaving the breast tissue otherwise intact). The team examines the records from five large hospitals and compares the survival times after surgery of all women who have had these various types of surgery for breast cancer.

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Question 4 1 pts Was this study
Was this study
a randomized controlled design experiment
an observational study
a survey
None of the above

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Question 5 1 pts What was the explanatory (treatment) variable?
What was the explanatory (treatment) variable?
Hospital
Survival time
Form of mastectomy
Woman

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Question 6 1 pts What was the response variable?
What was the response variable?
Hospital
Survival time
Form of mastectomy
Woman

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Question 7 1 pts What was the experimental unit?
What was the experimental unit?
Hospital
Survival time
Form of mastectomy
Woman

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Question 8 1 pts Skip to question text.
A public health research wants to determine the average blood lead concentration for children in elementary school (grades K through 5), but has reason to believe the concentration may differ among neighborhoods where predominantly lower, middle, and upper socio-economic class populations live.
Select the most appropriate sampling or experimental study design for the above situation.
Natural experiment (observational study)
Stratified sampling
Systematic sampling
Cluster sampling

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Question 9 1 pts Skip to question text.
A health and nutrition researcher wants to determine if people who are on a calorie-restriction diet and do an hour of aerobic exercise three days per week lose more weight than people who just restrict caloric intake, people who just exercise, and people who do neither.
Select the most appropriate sampling or experimental study design for the above situation.
Natural experiment (observational study)
Stratified sampling
Systematic sampling
Cluster sampling

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Question 10 1 pts Skip to question text.
A student in a wildlife biology class wants to determine the abundance of a rodent species in a local nature preserve, divided into smaller blocks. She is concerned that she only has a modest number of traps and time to do the project, and wants to select the most appropriate sampling or experimental study design. Which one of the following is most appropriate for this study?
Natural experiment (observational study)
Stratified sampling
Systematic sampling
Cluster sampling