
●
Accept the default option to t the data to a straight line.
●
Choose a predened t type (logarithmic, exponential, and so on).
●
Enter your own mathematical expression. The expression will be plotted so that you can see how closely
it ts the data points.
Choosing a t
1.
Press to display the Symbolic view.
2. For the analysis you are interested in (S1 through S5), select the Type eld.
3. Tap the eld again to see the menu of t types.
4. Select your preferred t type from the menu. (See Fit types on page 254.)
Fit types
Twelve t types are available, as follows:
Fit type Meaning
Linear (Default.) Fits the data to a straight line: y = mx + b. Uses a least-squares t.
Logarithmic Fits the data to a logarithmic curve: y = m lnx + b.
Exponential
Fits the data to the natural exponential curve: y = b * e
mx
Power
Fits the data to a power curve: y = b * x
m
Exponent
Fits the data to an exponential curve: y = b * m
x
Inverse Fits the data to an inverse variation: y = m/x + b
Logistic
Fits the data to a logistic curve: where L is the saturation value for
growth. You can store a positive real value in L, or—if L = 0—let L be computed automatically.
Quadratic
Fits the data to a quadratic curve: y = ax
2
+ bx + c. Needs at least three points.
Cubic
Fits the data to a cubic polynomial: y = ax
3
+ bx
2
+ cx + d
Quartic
Fits to a quartic polynomial: y = ax
4
+ bx
3
+ cx
2
+ dx + e
Trigonometric Fits the data to a trigonometric curve: y = a * sin(bx + c) + d. Needs at least three points.
User Dened Dene your own t (see the following).
Dening your own t
1.
Press to display the Symbolic view.
2. For the analysis you are interested in (S1 through S5), select the Type eld.
3. Tap the eld again to see a menu of t types.
4. Select User Dened from the menu.
254 Chapter 12 Statistics 2Var app
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