You design an experiment to test the effectiveness of a vaccine against a strain of influenza. In the experiment, 100,000 people receive the vaccine and another 100,000 people receive a placebo. Identify a potential problem with the experimental design. Then describe how you can improve it.

Listed below are nine technical accounting terms used in this chapter:

$$\begin{array}{lll}\text { Unrecorded revenue } & \text { Adjusting entries } & \text { Accrued expenses } \\ \text { Book value } & \text { Matching principle } & \text { Accumulated depreciation } \\ \text { Unearned revenue } & \text { Materiality } & \text { Prepaid expenses }\end{array}$$

Each of the following statements may (or may not) describe one of these technical terms. For each statement, indicate the accounting term described, or answer "None" if the statement does not correctly describe any of the terms.
f. A type of account credited when customers pay in advance for services to be rendered in the future.

Design an experiment that would test the ability of fern gametophytes to grow on different soils.

The United States Postal Service delivers about

$$2 ^ { 8 } \cdot 5 ^ { 2 }$$

pieces of mail each second. There are

$$2 ^ { 8 } \cdot 3 ^ { 4 } \cdot 5 ^ { 2 }$$

seconds in 6 days. How many pieces of mail does the United States Postal Service deliver in 6 days? Write your answer as an expression involving powers.

Design an experiment to demonstrate the actions of the sympathetic and parasympathetic nervous systems on the iris of the eye.

A design change is required in the valve interface circuit of the temperature-control system shown . The new design will have a valve interface input resistance of $10 \mathrm{k} \Omega$. Determine the effect this change has on the temperature-to-voltage conversion circuit.

How did the creation of the Fed improve our banking system?

Understanding the evolution of our banking system is important because it helps us understand the features of modern banking. Today we have a managed money supply that is accepted by everyone simply because people have faith in it. Which of the following is true about our banking system today?

a) Most of our money circulates as coins and paper currency.

Fill in the blanks with an appropriate word, phrase, or symbol(s). When the denominator of a fraction contains no radical expressions, it is said to be _.

Insert a colon where necessary. If the sentence is correct, write C in the blank.
______The most popular sports in the United States are football, basketball, and baseball.

The resolution limit of a microscope is roughly equal to the wavelength of light used in producing the image . Electron microscopes use an electron beam (in place of photons) to produce much higher resolution ima ges, about 0.20 nm in modern instruments. Assuming that the resolution of an electron microscope is equal to the de Broglie wavelength of the electrons used, to what speed must the electrons be accelerated to obtain a resolution of 0.20 nm?

Modern jet engines have vanes that are deployed to produce a reverse thrust just after a plane touches down on a runway. The air flow rate through a particular engine is $100 \mathrm{~kg} / \mathrm{s}$, and the combustion gases exit the engine at a speed of $800 \mathrm{~m} / \mathrm{s}$ relative to the engine. The fuel-air ratio is 1 to 40 in this case. Calculate the reverse thrust produced by the vanes for the configuration shown.

Design an experiment to find out the effect of water temperature on frog egg development.

Write the following sets:

(a) The set of letters used in the sentence “List the elements in a set only once.”

(b) The set of letters that are needed to spell these words: team, meat, mate, and tame

(c) The set of states in the United States that contain the letter Q

In many of the world’s poorest countries, nearly 50 percent of the population is under 15 years of age. If these people are to help improve the productivity of their economies, they must be trained in modern methods of production. In 2000, just over 4 million of the 8.8 million people of Chad were under 15. Explain why it would be difficult for many of these children to be educated and become productive members of a growing economy.