Develop the Null and Appropriate Hypotheses That Are Most Appropriate

Develop the null and appropriate hypotheses that are most appropriate for each of the following situations:
A meteorologist claims that the average high temperature for the month of August in Chicago, Illinois is 83°F. If the residents of Chicago do not believe this to be true, what hypotheses should they test?
H₀: ______________
H₁: ______________
A car manufacturing plant is acting in accordance with the public's interest in making cars that have gas mileage of at least 28 miles per gallon. The supervisor will only let the cars off the manufacturing floor if the gas mileage is more than 25 miles per gallon. What hypotheses should the plant test?
H₀: ______________
H₁: ______________
A spokesperson for the Health Department reports that a fish is unsafe for human consumption if the polychlorinated biphenyl (PCB) concentration exceeds 5 ppb. The Carlson family is interested in the mean PCB concentration in a fish from the lake on which they live. What hypotheses should they test?
H₀: ______________
H₁: ______________
An Internet survey revealed that 50% of Internet users received more than 10 e-mail messages per day. A similar study on the use of e-mail was repeated. The purpose of the study was to see whether use of e-mail has increased.
H₀: ______________
H₁: ______________