Model Trendline Multi Excel 2013V0F 1

byMilo Schield

Member: International Statistical Institute

US Rep: International Statistical Literacy Project

Director, W. M. Keck Statistical Literacy Project

Slides at: www.StatLit.org/pdf

/Model-Trendline-Multi-Excel2013-6up.pdf

Model Using Trendline Non-Linear in Excel 2013

Model Trendline Multi Excel 2013V0F 2

Goal: Summarize association between two variables

1. Generate seven charts showing association between two quantitative variables (slides 5-11).

2. Use seven different models: linear with forecast, linear with intercept = 0, polynomial, logarithmic, power, exponential and moving average.

3. For each chart (except moving average), show trend-line, regression equation and R2. Show title and axis for all

4. Review comparison of model R-squared on slide 12. No description of association (trend) is necessary.

For details on using Trendline to build a model, see> www.StatLit.org/pdf/

Model-Trendline-Linear-Excel2013-6up.pdf

Model Trendline Multi Excel 2013V0F 3

Using Chart TrendlineCreate Graph. Look for + Sign

.

Select Chart Elements. Check Trendline box. Select More Options.

Select Algebraic model Check Equation & R-square[Check Forecast or Intercept]

Model Trendline Multi Excel 2013V0F 4

Algebraic Models

1) Linear: Y=a+bx. Straight line, simplest

2) Polynomial: Y= a+bx+cx2. Multiple curves

3) Logarithmic: Y=aLn(x)+b. Ratio scale. Equal ratios have equal differences Log10(1) = 0; Log10(10) = 1; Log10(100) = 2

4) Power model: Y=axb [Between log & exp.]

5) Exponential: Y=aex/b. Constant rate of change

6) Moving average: For time series

Model Trendline Multi Excel 2013V0F 5

1) Linear Model w Forecast

Model Trendline Multi Excel 2013V0F 6

1) Linear Model: Intercept = 0

Model Trendline Multi Excel 2013V0F 7

2) Polynomial Model

Model Trendline Multi Excel 2013V0F 8

3) Logarithmic Model

Model Trendline Multi Excel 2013V0F 9

4) Power Model

Model Trendline Multi Excel 2013V0F 10

5) Exponential Model

Model Trendline Multi Excel 2013V0F

80100120140160180200220240

60 62 64 66 68 70 72 74 76

Wei

ght (

lbs)

Height (Inches)

Moving Average (2 period) of Wt by HtData must be sorted by Height & Weight

Cannot create Equation or R-squarefor Moving Average.

11

,

Model Trendline Multi Excel 2013V0F 12

Comparison of R-squared

Percentage of Weight “explained by” Height• 61.6% Linear model• 40.6% Linear (intercept = 0) << Worst fit• 62.1% Polynomial model• 61.2% Logarithmic model • 63.1% Power model• 63.3% Exponential model << Best fit!No equation/fit for Moving-Average model.