A control variable is a variable included in a regression equation whose purpose is to:
A. improve the fit of the model.
B. provide a placebo test.
C. ensure the sample is representative.
D. alleviate an endogeneity problem.
Answer: D
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A(n) ________ is the ring of cytoplasm lining the plasmodesmata.
Fill in the blank(s) with the appropriate word(s).
When a bacterium is introduced to a new environment with plenty of nutritional resources, binary fission will allow for rapid growth of the population (2-4-8-16-32-64 . . . etc.). However, there is usually a slight lag before the rapid growth begins. What is the best explanation for this lag period?
A. Binary fission becomes more and more efficient after each cell division. B. It takes time to induce and amplify the production of the enzymes needed for binary fission. C. Structural genes act more slowly than metabolic genes. D. It takes time for bacterial cells to duplicate enough organelles to digest new media. E. The new media contains compounds that turn on repressor proteins.
About 4% of people of northern European descent are carriers for an autosomal recessive genetic disorder in which a defective membrane transport protein leads to abnormal chloride levels in extracellular fluids. What is the name of this disorder?
a. Duchenne muscular dystrophy b. cystic fibrosis c. achondroplasia d. sickle cell anemia
Ames test is a tool approved by FDA to detect potential carcinogens.
A. True B. False