Question

How much should a healthy Shetland pony weigh? Let x be the age of the pony (in months), and let y be the average weight of the pony (in kilograms).

x	3	6	12	15	25
y	60	95	140	172	175

(a)

Make a scatter diagram of the data and visualize the line you think best fits the data. (Submit a file with a maximum size of 1 MB.)

quiz pony.xlsx

(b)

Would you say the correlation is low, moderate, or strong?

lowmoderate    strong

Would you say the correlation is positive or negative?

positivenegative    

(c)

Use a calculator to verify that Σ(x) = 61, Σ(x²) = 1039, Σ(y) = 642, Σ(y²) = 92,434, and Σ(x y) = 9,385.

Compute r. (Enter a number. Round your answer to three decimal places.)


As x increases from 3 to 25 months, does the value of r imply that y should tend to increase or decrease? Explain your answer.

Given our value of r, y should tend to remain constant as x increases.Given our value of r, we can not draw any conclusions for the behavior of y as x increases.    Given our value of r, y should tend to increase as x increases.Given our value of r, y should tend to decrease as x increases.

Answer 1

a)

b) correlation is strong (since almost all the points appear to fall nearer to a line)

correlation is positive( since trend is upward)

c)

from above:

ΣX =	61.000
ΣY=	642.000
ΣX2 =	1039.000
ΣY2 =	92434.000
ΣXY =	9385.000
r =	0.904

Given our value of r, y should tend to increase as x increases