In a case-control study of computer display exposure and glaucoma, cases and controls were also asked about television watching habits. Errors in recall of exposure to video screens occurred with equal frequency among cases and controls. Which of the following methods for adjusting for confounding by age is most likely to affect the generalizability of the study findings?

a. Randomization
b. Restriction of study subjects to those less than 50 years old
c. Stratification to several age groups
d. Matching by age plus or minus 5 years
e. Adjustment for age in a regression analysis

Elements and compounds are pure substances that cannot be broken down physically into a simpler substance. a physical change doesn’t break the bonds between atoms of a substance or form new ones. compounds can be broken down by a chemical change. a chemical change breaks chemical bonds and/or forms new ones between atoms of a substance. what simple substance would a compound break into? the basic elements that make it up! for example, if you passed a very strong electric current through water you’d break the chemical bonds in water and be left with oxygen and hydrogen. which of the following is an example of a chemical change? a separating water into different glasses b breaking frozen ice cubes with a hammer c running an electric current through water d boiling water to evaporate it on a stove

Classify the structures as homologous or analogous, depending on their structure and function.

Which kind of worm has a closed circulatory system? a planarian b fluke c pinworm d an earthworm