Question

A data set comparing a woman's shoe size to her height is represented by the table.

Shoe Size Height (inches)
7 60
9 72
10 65
7 68
9 69.5
10 70
12 75
12 61
13 68


What is the equation for the line of best fit for a woman's height, y, based on her shoe size, x?
y = −0.49x + 62.8
y = 0.49x + 62.8
y = 0.65x − 69.5
y = −0.65x − 69.5

Answer 1

y = 0.49x + 62.8

Explanation:

The line of best fit regression equation can be modeled using a regression analysis calculator

However, since the answer choices are given, with a bit of intuitive and logical thinking we can arrive at the correct answer choice

Let's eliminate the last answer choice: y = −0.65x − 69.5

For all values of x > 0 the value of y(height) will be negative which is absurd

The second-last(3rd answer choice) can also be eliminated. At x = 10
y = 0.65(10) - 69.5 = - 6.5 - 69.5 = - 64. The y-value is negative for all shoesizes shown

First choice seems reasonable:
However because of the -0.49x factor the height decreases as shoe size increases. This is counter-intuitive. Taller women tend to have bigger feet

Therefore the only correct answer choice is the second one:
y = 0.49x + 62.8

which shows a positive correlation between x and y