Chapter CSB1.5, Problem 1E

To determine

Plot a graph of linear regression of cellphone user of United States from 1985 to 2007.

Answer to Problem 1E

In 2015 there were 300 million users of cellphone.

Explanation of Solution

Given data:

Table ofcellphone user of United States from 1985 to 2007.

Formula used:

Slope intercept form:

  $y=mx+C$

Where $m=\frac{y_2-y_1}{x_2-x_1}$

Calculation:

Graph of cellphone user of United States from 1985 to 2007:

  

So the equation for this graph will be

  $\begin{array}{l}m=\frac{y_2-y_1}{x_2-x_1}\\ m=\frac{158.7-3.5}{2003-1989}\\ m=11.1\\ \end{array}$

Where,

  $\begin{array}{l}y=mx+C\\ 158.7=11.1(2003)+C\\ C=-22074.6\end{array}$

Equation is $y=11.1x-22074.6$

Year in which users are 300 million:

  $\begin{array}{l}y=11.1x-22074.6\\ 300=11.1x-22074.6\\ x=2015\end{array}$

Conclusion

In 2015 there were 300 million users of cellphone.