# Quarterly sales for a department store over a six-year period are given in the file P12_52.xlsx. a.

## Question:

Quarterly sales for a department store over a six-year period are given in the file P12_52.xlsx.

**a. **Use multiple regression to develop an equation that can be used to predict future quarterly sales. (*Hint*: Use dummy variables for the quarters and a time variable for the quarter number, 1 to 24.)

Let *X* represent the quarter number (1-24).

Let *X*_{1} represent a dummy for first quarters.

Let *X*_{2} represent a dummy for second quarters.

Let *X*_{3} represent a dummy for third quarters.

If required, round your answers to one decimal place. For subtractive or negative numbers use a minus sign even if there is a + sign before the blank. (Example: -300)

*Ŷ* =______ + _______ *X* +_______ *X*_{1} +_______ *X*_{2} +________ *X*_{3}

b. Letting Yt be the sales during quarter t, discuss how to estimate the following equation for this series.

Yt= abt1b2x1b3x2b4x3

Here X is a quarter, X1 is a dummy for first quarters, X2 is a dummy for second quarters, and X3 is a dummy for third quarters.

**c. **Based on your answer in part **b** develop a model that can be used to predict the logarithm of future quarterly sales.

Here *X* is a quarter, *X*_{1} is a dummy for first quarters, *X*_{2} is a dummy for second quarters, and *X*_{3} is a dummy for third quarters.

If required, round your answers to three decimal places. For subtractive or negative numbers use a minus sign even if there is a + sign before the blank. (Example: -300)

*LogŶ* = ______ +______ *X* +________ *X*_{1} +________ *X*_{2} +________ *X*_{3}

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**Related Book For**

## Elementary Statistics Picturing the World

ISBN: 978-0321911216

6th edition

Authors: Ron Larson, Betsy Farber