Core question

[khalil]

Seasonal indices

Autumn: 0.42
Winter: 0.51
Spring: 1.32
Summer:1.75

Sam sells 27 surfboards during winter and he is keen to do better that this in spring. Using the seasonal indices, the minimum number of surfboards Sam must sell in spring to improve on his winter sales is .....ans 70

I have no idea how to approach this question. Please help

[xXNovaxX]

Got it

Actual Figure= deseaosnlsied figure TIMES seasonal index  =       27* 1.32=35.64

Below is the deseasonalised figure
actual figure/seasonal index of winter since we are trying to improve on his Winter sales

35.64/0.51         
=69.8824
=70

(sorry for such a vague explanation if you can even call it that, I did have a thought process, but i accidentally lost my workings out, and forgot where and why i started, so had to quickly restart.)

[khalil]

Thanks bro, but can u also include your thought process, cos' i dont understand why we have to find the deseasonalised figure!

[ReVeL]

Basically, to compare things sold in seasons with each other we must de-seasonalise the data for our comparisons to have any meaning. For example, there is no use in comparing ice creams sold in winter vs summer. Even if we had an excellent winter by our standards, summer would inevitabley show larger sales. So as Nova stated we use the equation:

Actual Figure = Deseasonalised Figure x Seasonal Index

Now, all the seasonal indicies have been provided. If Sam sells 27 surfboards in winter then the de-seasonalised figure will be:



So, what we are looking for is for the deseasonalised figure in spring to be at least . Referring back to that equation, we can subsitute two knows and solve for the unknown to find the unseasonalised figure (i.e. amount of sales) in spring to better the performance in winter.





So, to exactly equal the performance of selling 27 surfboards in winter, Sam must sell 69.88 in spring. But, to improve he must sell more than 69.88. That is, he must sell at least 70.

Hope that helps.


EDIT: Typo.

[xXNovaxX]

oooo then i have nooooo idea what I was doing to get the same answer :S. I must have been wrong.

[khalil]

Thanks ReVel

[khalil]

I heard its possible to identify an outlier using mean and s.d. If true, how?