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Intermediate Algebra – Student Workbook – Second Edition 2013

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Lesson 4b <strong>–</strong> More on Logarithms<br />

Mini-Lesson<br />

Modeling Data with Logarithmic Regression<br />

Just as we did with Linear and Exponential Functions, we can model appropriate data using<br />

regression. The steps are very similar to the other processes we have used. We will use a slightly<br />

different type of logarithm for this regression denoted by LN or Natural Logarithm. You will<br />

learn more about this in later classes.<br />

Problem 10<br />

WORKED EXAMPLE <strong>–</strong> LOGARITHMIC REGRESSION<br />

Determine if the data set below can be modeled by a logarithmic function. If so, find that<br />

function rounding all decimals to 4 places.<br />

x .5 1 2 3 4 5<br />

y -10 .8 4.3 6.2 7.1 8<br />

Step 1: Insert data into L1, L2 list using Stat>Edit.<br />

Your data should look the same as in the table on<br />

the right.<br />

Step 2: Turn on your Plot (Go to Y= and highlight<br />

Plot 1) then select Zoom9 to work with a good<br />

window for your data. Your graph should look the<br />

same as the table on the right.<br />

The data are increasing but at a decreasing rate and<br />

generally have the shape of a logarithmic graph. We<br />

should be able to model the data effectively with a<br />

logarithmic equation.<br />

Step 3: Go to Stat>Calc>9:LnReg to find the<br />

Logarithmic Regression model for the data.<br />

Step 4: Press Enter twice to form the equation<br />

information on your screen. Write the equation as<br />

y = -2.2274 + 7.2698 Ln x<br />

Step 5: Enter the equation into your Y= list and<br />

press Graph to show the graph of the data and the<br />

model.<br />

Looks like the model is a pretty good<br />

approximation of our data set.<br />

Scottsdale Community College Page 171 <strong>Intermediate</strong> <strong>Algebra</strong>

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