Seasonality Analysis
Seasonality refers to recurring variations of a value at certain periods
(month, quarter, etc.) of the year. The demand for certain products
will peak at specific times of the year. Some products may peak
during the summer while others may peak during the winter.
Calculating a seasonal index can help identify seasonal patterns. The
seasonal index is calculated as the ratio of the average value in a
season (month, quarter, etc.) to the overall annual average value.
Create the following table. Name the Excel worksheet as
WHI_RoomsUsername.
Cell D29: Calculate the average monthly rooms. For the two year
period, the individual monthly rooms are found in cells D5:D28.
Round off the average so that the value is to the nearest whole number
– the same as the other values in the column. The value is 685.
Cell E5: For the first month, calculate the ratio of the monthly rooms
(D5) to the monthly room average (D29). Because only D29 contains
the monthly room average, the cell address needs to be absolute
($D$29). Round off to the nearest thousandth (3 decimal places).
This calculation compares for each month the number of rooms rented
with the average monthly rooms. Whenever this ratio is above 1,
Windy Hill Inn had rented more rooms than average for that month.
Whenever this ratio is below 1, Windy Hill Inn had rented fewer
rooms than average for that month.
Copy the formula down to cell D28. Format to show 3 decimal places.
Cell F5: The final step is to calculate the seasonal index, which is the
average of the rooms rented for each individual season (month). For
the first seasonal index, calculate the average the January ratios. The
January ratios are found in cells E5 and E17. Round off to the nearest
thousandth (3 decimal places). Format to 3 decimal
Create a line graph to show the monthly trend in the seasonal index.
The reason a type line graph is used is because the X-data (Jan, Feb,
etc.) are non-numerical. Format the Y axis (vertical) to set the
minimum to 0.5, the maximum to 1.5, major units of 0.1, and the
horizontal axis crosses at a value of 1. Include an appropriate graph
title and axis titles.
Windy Hill Inn
Seasonal Index
Monthly Seasonal Index of Rooms Rented (2011-2012)
Copy down to cell E16. Complete the table.
1.500
1.400
1.300
1.200
1.100
1.000
0.900
0.800
0.700
0.600
0.500
Jan Feb Mar Apr May Jun
Jul Aug Sep Oct Nov Dec
Month
For which month does the number of rented rooms at Windy Hill Inn
come closest to representing the average monthly rented rooms?
Create a new Excel Worksheet, named WHI_DinnerUsername.
D21: Calculate the average quarterly dinner guests. Round off to the
nearest whole number.
E5: Calculate the ratio of the first quarter’s dinner guests to the
quarterly average dinner guests. Round off to the nearest thousandth.
Format. Copy down to cell E20.
F5: Calculate the seasonal (quarterly) index by calculating the average
of all first quarter dinner guests. Round off to the nearest thousandth.
Format. Copy down to cell F8.
Complete the table.
Create a graph to show the trend in the quarterly (seasonal) index for
each quarter of the year (First, Second, Third and Fourth). Format the
Y axis (vertical) to set the minimum to 0.5, the maximum to 1.5, major
units of 0.1, and the horizontal axis crosses at a value of 1. Include an
appropriate graph title and axis titles.