TI-85 STATISTICAL DATA ANALYSIS

• Set calculator default values
  Run Defaults Program
  1. ON
  2. PRGM
  3. NAMES (F1)
  4. Defaults

Caution: clears all data stored in lists and restores default calculator values

• Enter lab data into lists on the calculator

2nd - (LIST) EDIT (F4) enter name for your list enter values EXIT
2nd - (LIST) EDIT (F4) enter name for your list enter values EXIT

-you can use unique names

-notice how your list now become "options" on the option bar at the bottom of the screen.

• Setup your calculator to analyze the data.

STAT CALC (F1) Choose name for Xlist from option bar Down Arrow Choose MORE for more examples Select Ylist option ENTER ENTER

• Determine the regression model that "best fits" your data

Your are looking for the statistical model with the highest correlation coefficient (r)

The models to choose from are:

Linear regression y = ax + b LINR Log regression y = a+b ln x LNR Exponential regression y = ab^x EXPR Power regression y = ax^b PWR

Choose the model using the option bar (F1, F2, etc.)

Calculate all of the models to decide which fits your data. Make your decision based upon the correlation coefficient (corr). The model who's correlation is closest to 1 or -1 "best fits" your data.

example:

Model	Key strokes	Screen picture	Results
Linear regression	F2		"Best Fits"
Log regression	F3
Exponential regression	F4
Power regression	F5

In this case, linear regression is the obvious model. Calculate LINR again and move to the next step.

• Set window range values.
  Run RANGE Program

EXIT EXIT PRGM NAMES (F1) choose RANGE ENTER 2nd LIST NAMES (F3) choose Xlist name ENTER 2nd LIST NAMES (F3) choose Ylist name ENTER

• Plot data and draw regression line

STAT DRAW (F3) SCAT (F2) draw scatter plot DRREG(F4) draw regression EXIT EXIT (returns to home screen)

• Interpolation and extrapolation

STAT DRAW (F3) FCST (forecast) enter an X value or a Y value move cursor to the unknown value SOLVE (F4) EXIT

STORAGE & RECALL OPTIONS

(use only if you wish to use graph and/or database at a later date)

Store graph picture GRAPH MORE MORE STPIC (F2) (store picture) name picture ENTER	Recall graph picture STAT DRAW (F3) CLDRW (F5) clear draw MORE RCPIC (F3) (recall picture) choose picture name ENTER
Store graph database GRAPH MORE STGDB (F4) name database ENTER	Recall graph database GRAPH MORE RCGDB (F4) choose database name ENTER

Example Problem:

Time (minutes) Amount (grams) 2 3 4 8 12 24 16 12 6 4

Determine the model, plot the line of "best fits" and answer the following questions.

1. What is the equation for the line of best fits?
2. What is the amount present at 5 minutes?
3. At what time would 25.1 grams remain?

Solution & Help

Questions: