Question 698727: AJ used linear regression to help him understand his monthly telephone bill. The line of best fit was y=23.65 + 1.28 x.
A. Explain the meaning of the y intercept in terms of the bill.
B. Explain the slope of the line in terms of the telephone bill.
Answer by Positive_EV(69)   (Show Source):
You can put this solution on YOUR website! For any equation in the form y = mx + b (including the results of a regression), the value of b is what y equals when x = 0. So, for this regression, the y-intercept, 23.65, is what the regression estimates AJ would pay if he didn't use his phone at all (that is, x = 0). Since this is a regression line, this doesn't definitely indicate what AJ would pay if he didn't use his phone, it's just the best estimate based on the data.
For a regression line, the slope represents the increase (if positive, if the slope is negative it would be a decrease) in the expected value of the dependent variable y for an increase of 1 in the independent variable x. In this equation, if AJ uses his phone for 1 additional minute (the unit of x isn't specified, but I'll assume it's in minutes), he can expect his phone bill to increase by $1.28. Again, since this is a regression this is a best estimate and not a definite value.
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