[HELP] Dollar Graph

Question

The table shows the value y (in dollars) of a stock on day t. Use the regression feature on a graphing calculator to find a quadratic model and a cubic model for the data.

table

t: 1 2 3 4 5 6 7 8 9 10

y: 7.52 8.03 8.43 8.47 8.26 7.96 7.72 7.74 7.92 8.42

Which model is a better fit for the data?

a. Quadratic model

b. Cubic model

Enter the better-fitting model. Round each number to the nearest thousandth. y=?

Use the model to estimate the value of the stock on day 13 to the nearest cent.

Answer 1

This isn't really an algebra question - more stats or data analytics.

Nice that this question tells you what to do.

On your calculator (I'm using a TI-84) put the t values in L1 and y values in L2.

First, the quadratic regression: Stat-Calc-QuadReg: X is L1, Y is L2, Freq is blank, store equation in Y1 (use Vars key). a, b, and c are the coefficients of this quadratic equation.

Next, the cubic regression: Stat-Calc-CubicReg. Same deal. Store equation as Y2.

Go to StatPlot and turn on Plot1.

ZoomStat to see the points and the two equations.

Wow, I wonder which one is the better fit....

Use the equation from Y1 or Y2 to evaluate t=13.

Done!