A dumping site in the small town of Love Canal, New York, was used for the disposal of industrial chemical wastes from 1970-1975. In 1980, the housing inspector noticed traces of toxic substances in the basement walls of the local schools and homes. The local hospital noticed that there were 25% higher numbers of birth defects during 1970-1980. The hospital then offered free genetic tests and found that 20% of the adult volunteers/residents of Love Canal contained genetic abnormalities. The exposure to those industrial chemical wastes must have been the cause the genetic abnormalities and higher birth defect incidence. Your Interpretation:

There is no control group and variables were not addressed.

Explanation:

In the context, it is given that there is a dumping ground in a small town called Love Canal and harmful chemical waste of industries are dumped there. Lately, it is noticed that there were traces of the toxic substances on the walls of the schools and the hospitals. The hospitals also noticed that during the period of 1970 to 1980, there were increase in the number of the birth defects in the area. The people of the Love Canal has genetic abnormalities and the chemical waste is responsible for it.

Thus it can be concluded that there is a no such any control group in this case. The confounding variables like the comorbidities as well as the family history of the genetic defects were not addressed.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added