Correct Answer: D

Rationale: In this study, the dependent variable is the 'Average hours worked per week,' as it relies on the different types of 'Hospital Staff' (the independent variable). The amount of time worked per week varies based on the category of staff being considered. Therefore, the correct choice is D. Choices A and B incorrectly assign the dependent and independent variables to specific staff categories (Nurses and Physicians), which are actually different elements within the study. Choice C incorrectly defines the dependent variable as 'Hospital Staff,' when in fact, it is the 'Average hours worked per week' that is dependent on the type of staff.

Correct Answer: B

Rationale: The correct answer is B. In a double bar graph, Group A is positively skewed, meaning its data is clustered on the left and has a tail extending to the right. On the other hand, Group B displays a normal distribution where the data is evenly distributed around the mean. Choices A, C, and D are incorrect as they inaccurately describe the skewness and distribution of the data in Group A and Group B.

Correct Answer: C

Rationale: To calculate the final dosage, first find 1/5 of 310 mg, which is 62 mg, and subtract it from the original dosage. This gives 310 mg - 62 mg = 248 mg. Then, subtract an additional 20 mg from the result to get the final dosage: 248 mg - 20 mg = 228 mg. Therefore, the patient's final dosage is 228 mg. Choice A (20 mg) is incorrect because it only considers the second reduction of 20 mg and misses the initial reduction by 1/5. Choice B (42 mg) is incorrect as it miscalculates the reduction amounts. Choice D (248 mg) is incorrect as it does not account for the second reduction of 20 mg.

Correct Answer: B

Rationale: To find the percentage more staff members at Hospital Y are female than at Hospital X, we first calculate the percentage of female staff members at each hospital. For Hospital Y: (90 / 183) x 100 ≈ 49.2%. For Hospital X: (97 / 250) x 100 ≈ 38.8%. The difference between these percentages is approximately 10%, making choice B the correct answer. Choice A, 5%, is too low as the difference is greater. Choice C, 15%, and choice D, 20%, are both too high as the actual difference is closer to 10%.

Correct Answer: C

Rationale: To find the total amount contributed, you can add the individual contributions: $12.03 + $11.96 + $12.06 = $36. Therefore, the roommates used a total of $36 to purchase the gift. Choice A ($34), B ($35), and D ($37) are incorrect as they do not reflect the accurate total amount contributed by the roommates.