WEEK 8 ASSIGNMENT: CORRELATION AND CAUSATION CORRECT ANSWERS / ALREADY GRADED A

WEEK 8 ASSIGNMENT: CORRELATION AND CAUSATION CORRECT ANSWERS / ALREADY GRADED A Understand the difference between correlation and causation Question True or False: The more samples taken in a scientific study, the longer the amountof time it will take to complete the research on the samples. Although there are other factors that affect study time, such as experience and equipment, increasingthe number of samples will cause an increase in research time Correct! You nailed it. Understand the difference between correlation and causation Question Suppose that a large controlled experiment tests whether caffeine improves reaction times. A very large number of randomly selected participants are randomly given identical-seeming pills with varying doses of caffeine (including none) and then given tests of reaction times under the same conditions. The experiment finds a strong negative correlation between caffeine dose and reactiontime. (Note that lower reaction times are better.) Correct answer: Correlation alone does not prove causation, but this scenario provides more evidence than just correlation between two variables. Since the data were obtainedfrom an appropriately randomized controlled experiment, a correlation can be used as evidence of a causal relationship. Since all other variables were controlled,there is no third variable that could be associated with caffeine that actually causesdifferencesin reaction times. Yesthat's right. Keep it up! Interpret the slope and y-intercept of the least squares regression line Question Which of the following situations could have a regression line with a negative y-intercept? Select all that apply: Great work! That's correct. • The present value of an insurance policy as a function of the age of the ensured person if the person purchases the policy when he or she is 50years old. • • The number of millions of barrels of oil in an oil field as a function of thenumber of years the oil field has been in production. • • The value of a Fortune-500 company, founded in the year 1990, as a function of the number of years after the year 2010. • • The value of a rail locomotive as a function of the number of years since itwas put into service. Interpret the slope and y-intercept of the least squares regression line Question Which of the following data sets or plots could have a regression line with a negative slope? Select all that apply. Perfect. Your hard work is paying of f • The number of tons oftrash in a landfill as a function of the number of yearssince the landfill was built. • • The number of loads of trash a dump truck hauls per month as a function ofthe number of yearssince the dump truck was built. • • The number of tons of trash produced in a city as a function of thepopulation. • • The number of minutes you will wait to drop off yourtrash at a landfill as afunction of the number of dump trucks at the landfill Correct answer: The slope is related to the increase or decrease of the dependentvariable as a function of the independent variable. If the dependent variable can decrease, then the slope can be negative.