Statistics Homework

Choose two bivariate data sets, one with positive linear correlation and one with negative linear correlation. Collect at least 20 data pairs for each. Below are some examples, feel free to choose your own. Avoid using time as one of your variable.

• “Seahawks wins (x) vs Annual Rainfall in Seattle (y)”

• “Overall Quality (x) vs Level of Difficulty (y) on Rate my Professor”

• “Population of a city (x) vs Number of Starbucks (y)”

For each of your data sets:

(a) Use technology to plot your data set on a scatterplot. Make decisions about any outliers. Note if your data is possibly non-linear. (If the data set is definitely non-linear, find a new data set)

(b) Use technology to compute the correlation. Classify the correlation as strong/weak, positive/negative (or make a note that correlation may not be linear).

(c) Use technology to compute the equation of the line of best-fit. Describe what the slope of this line tells you. Use units. Describe what the y-intercept of this line tells you.

(d) When is this model valid? When does it break down and why?

(e) Use your model to extrapolate two data points not in your original data set.

(f) Describe the relationship between these two data sets. Is there cause and effect? Reverse cause and effect? Lurking variable? Coincidence?

(g) Summarize your findings.