Pyt N.
asked • 01/10/20What would be a scatter plot for this data? How to describe the correlation?
The table gives the number of one-pound loaves of bread you could buy for $1.00 in the United States for various years since 1900. Make a scatter plot of the data and describe the correlation shown.
Years since 1900, t 13 30 50 70 90 97
Loaves of bread, b 17.8 11.6 6.9 4.1 1.4 1.1
More
2 Answers By Expert Tutors
Edward A. answered • 01/10/20
Tutor
4.9
(17)
High School Math Whiz grown up--I've even tutored my grandchildren
Pyt,
A scatter plot is a graph where you don’t draw a line from one point to the next.
So, make a graph, making room for x to go between 0 and 100, and for y to go from 0 to 20.
Now, plot a point at (13, 17.8), another point at (30, 11.6), etc., six points in all.
You have now made the scatter plot.
Is your question about “correlation”? I don’t know whether the ACT or SAT cover the statistical concept “correlation coefficient”, so I cant tell you to use that.
The word “describe” connotes that they want simple words rather than precise numbers.
Imagine a straight line passing through the cloud of points; it doesn’t have to touch every point. Does the line slope downward or upward? Are the points far away from the line, or near it? Is there one point far away from the line? It would be called an “outlier”
Would a straight line be close to all the dots, or would a curve like a parabola be necessary to get near all the points?
The answers to these would constitute a description of how well correlated the two variables are (years since 1900, loaves per dollar)
Lenny D. answered • 01/12/20
Tutor
4.8
(563)
Former professor at Tufts University with decades on Wall Street
See the Video above
Still looking for help? Get the right answer, fast.
Ask a question for free
Get a free answer to a quick problem.
Most questions answered within 4 hours.
OR
Find an Online Tutor Now
Choose an expert and meet online. No packages or subscriptions, pay only for the time you need.
Stanton D.
So you are given 6 ordered pairs of data, each representing a year since 1900, and the loaves per $1 respectively. A scatter plot has these data as (x,y) points on an (x,y) Cartesian graph paper or equivalent, with year along the x axis, and # loaves along the y-axis. I say "along", but you know what I mean, as (x,y) points. The correlation describes whether or not the points lie along a straight line, whether (if so) the slope trend is positive or negative, and whether the trend is curved or straight, as far as you can detect. There's no reason to pull out physical graph paper, put the points into a spreadsheet and ask for the graph ("Chart" in most spreadsheets, and you must usually also choose "scatterplot" mode)! I don't believe you are being asked to give the correlation constant of the linear least-squares regression, so just do a qualitative statement. P.S. If you want to do a better job than that, say (1) why the graph is expected to be curved, (2) how you would have to transform the data in order to demonstrate a constant rate of inflation of prices over time, and (3) do what you said in (2). Hint: you do not have prices as your data, you have a measure of inverse of price. -- Cheers, --- Mr. d.01/10/20