You conduct a quasi-experiment to assess the impact of raising the speed limit from 55 to 65 miles per hour. You find that there are more accidents in the 6-month period following the speed limit change than in the 6-month period before the speed limit change. Although it is tempting to say that raising the speed limit caused higher accident rates, you must be careful because. A) you don't have an independent variable in this design. B) you have an adequate understanding of the operational definition of an "accident" C) other variables (for example, cheaper gasoline or the season of the year during which the change was instituted) may also be affecting accident rates. D) there is no problem with drawing this causal conclusion.

C) other variables (for example, cheaper gasoline or the season of the year during which the change was instituted) may also be affecting accident rates.

Explanation: Before making conclusion on causality, several other independent variables should be considered before arriving at a reasonable conclusion. Accident causing factors are numerous which could include, season of the year in which the change in speed limit was made, this may have a say in the weather condition which could impede vision, which could also result in accident , gasoline type, and other events which occurred within the speed change period which could have impacted the accident rate should be considered before arriving at a conclusion.

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two jet streams that directly affect the formation of weather in the continental part are a polar jet and a subtropical jet. they are responsible for the transportation of weather systems, which directly affect people. the polar front is the boundary between cold air from the north pole and warmer equatorial air. both the polar jet and the subtropical jet blow from the west to the east, and follow the boundary between cold and warm air.

the strongest jet streams are polar jets, while subtropical jets are somewhat weaker.

the right answer is c. the polar jet stream is generaly stronger than the subtropical jet stream.