Question

An equation was used to predict possible weights of puppies at 6 months of age. The actual weights of the puppies are also listed.


Actual weight (ounces) 9 15 16 20 20 26
Predicted weight (ounces) 9 12 15 18 21 24


The sum of the residuals is ______.

Answer 1

@phi @nincompoop @mathmate

Answer 2

@just_one_last_goodbye

Answer 3

@MrNood

Answer 4

I was thinking it could be 2

Answer 5

A residual of an observation is the algebraic difference (i.e. carries a sign) between the observation and the predicted value, equal to
e=x-xhat
where e=residual
x=observed value
xhat is predicted value.

The sum of the residual is obtained by adding up residuals of all observations.

If the prediction equation models the data well, the \(sum\) of the residuals should be relatively small.

Answer 6

As an example, for the last observation, the residual is
residual, e = actual weight-predicted weight = 26-24=2 oz

Answer 7

Thanks!

Answer 8

It wasn't 2 btw -_-

Answer 9

The "2" in the example is just one single observation (the last).
The proper answer is the total of all residuals, i.e. total of the residuals for all observations.
Hope that clarifies a little.