Forecast, Logest or Linest?

[Q706003]

Hi Guys

I am trying to set up a spreadsheet using either Forecast, Logest or Linest to estimate future kit receipt numbers using past data of units sent and units returned and i am having problems, first of all is this possible using the data below with any of these functions in Excel? And secondly, any tips to help me along?

Month .........................Kits Shipped ..................Kits Returned
JAN.............................78000............................31252
FEB ............................100124 ..........................32657
MAR ...........................103012 ...........................41135
APR ............................90560 .............................37122
MAY ...........................92104..............................37498
JUN ............................89281 ..............................40357
JUL..............................86234...............................?????

 

[brettdj]

You would be best off graphing the relationship as a X Y scatter plot (shipped v returned), and inserting trendlines to measure the strength of any relationship. Also do youe expect the season to impact shipping, or the returned/shipping ratio

You could chart

- linear
- log
- ln
- quadtratic etc

If you were to use a function use LINEST, as you can use it to fit polynomials, log relationships, ln relationships etc. It can also return the regression fitting stats

But charts are easier for the human eye to understand

Cheers

Dave

 

[tusharm]

The type of trendline you use depends on an understanding of the underlying issues and cannot be dictated from "outside." In your case you probably also have to account for seasonality.

For more information on trendlines see
Regression Analysis
http://www.tushar-mehta.com/publish_train/data_analysis/16.htm

Hi Guys

I am trying to set up a spreadsheet using either Forecast, Logest or Linest to estimate future kit receipt numbers using past data of units sent and units returned and i am having problems, first of all is this possible using the data below with any of these functions in Excel? And secondly, any tips to help me along?

Month .........................Kits Shipped ..................Kits Returned
JAN.............................78000............................31252
FEB ............................100124 ..........................32657
MAR ...........................103012 ...........................41135
APR ............................90560 .............................37122
MAY ...........................92104..............................37498
JUN ............................89281 ..............................40357
JUL..............................86234...............................?????