MATH 225N Week 8 Assignment: Correlation and Causation
Understand the difference between correlation and causation
Question
True or False: The more samples taken in a scientific study, the longer the amount of 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, increasing the 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
reaction time. (Note that lower reaction times are better.) Correct answer:
There is evidence that caffeine causes lower (better) reaction times.
Correlation alone does not prove causation, but this scenario provides more evidence than just
correlation between two variables. Since the data were obtained from 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 causes differences in reaction times. Yes that'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 50 years old.
The number of millions of barrels of oil in an oil field as a function of the number 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 it was put into service.
Understand the difference between correlation and causation
Question
True or False: The more samples taken in a scientific study, the longer the amount of 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, increasing the 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
reaction time. (Note that lower reaction times are better.) Correct answer:
There is evidence that caffeine causes lower (better) reaction times.
Correlation alone does not prove causation, but this scenario provides more evidence than just
correlation between two variables. Since the data were obtained from 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 causes differences in reaction times. Yes that'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 50 years old.
The number of millions of barrels of oil in an oil field as a function of the number 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 it was put into service.
