12. Barium sulfate, BaSO4, is a white crystalline solid that is insoluble in water. It is used by doctors to diagnose problems with the digestive system. Barium hydroxide,
Ba(OH)2, is also a white crystalline solid and is used in wastewater treatment.
How many more oxygen atoms are represented in the formula for barium sulfate
than in the formula for barium hydroxide?

Aresearch study is studying the effects of a new drug for osteoporosis alzheimer's disease (ad) for women above the age of 65 years. a group of individuals with osteoporosis is randomized into two groups. one group is treated conventionally, and the second group is treated with the new medication. assessments are made at 3, 6, 12, 36, and 48 months. the conventionally treated group is assessed for ad using a serum blood test, and the treatment group is assessed for ad using a pet radiotracer that binds to beta-amyloid plaques. in comparing these 2 trial arms, the authors of the study may encounter which type of bias? a. selection bias on the risk of developing b. measurement bias c. confounding bias d. recall bias e. lead-time bias