按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
observations will be observed in a span of six standard deviations； three
below the mean and three above the mean。 The standard deviation is an
amount calculated from the values in the sample。 Use this calculator （
easycalculation/statistics/standard…deviation。php） to work out the
standard deviation by entering the numbers in your sample。
Forecasting
Sales drive much of a business’s activities； it determines cash flow； stock
levels； production capacity and ultimately how profitable or otherwise a
business will be； so； unsurprisingly； much effort goes into a。。empting to
predict future sales。 A sales forecast is not the same as a sales objective。 An
objective is what you want to achieve and will shape a strategy to do so。 A
forecast is the most likely future oute given what has happened in the
past and the momentum that provides for the business。
The ponents of any forecast are made up of three ponents and to
get an accurate forecast you need to depose the historic data to be。。er
understand the impact of each on the end result：
。 Underlying trend： This is the general direction； up； flat or down； over
the longer term； showing the rate of change。
。 Cyclical factors： These are the short…term influences that regularly superimpose
themselves on the trend。 For example； in the summer months
you would expect sales of certain products； swimwear； ice creams and
suntan lotion； for example； to be higher than； say； in the winter。 Ski
equipment would probably follow a reverse pa。。ern。
。 Random movements： These are irregular； random spikes up； or down；
caused by unusual and unexplained factors。
Using averages
The simplest forecasting method is to assume that the future will be more
or less the same as the recent past。 The two most mon techniques that
use this approach are：
。 Moving average： This takes a series of data from the past； say the last
six months’ sales； adds them up； divides by the number of months and
uses that figure as being the most likely forecast of what will happen
in month 7。 This method works well in a static； mature marketplace
where change happens slowly； if at all。
。 Weighted moving average： This method gives the most recent data more
significance than the earlier data since it gives a be。。er representation of
Quantitative and Qualitative Research and Analysis 253
current business conditions。 So before adding up the series of data each
figure is weighted by multiplying it by an increasingly higher factor as
you get closer to the most recent data。
Exponential smoothing and advanced
forecasting techniques
Exponential smoothing is a sophisticated averaging technique that gives
exponentially decreasing weights as the data gets older and conversely
more recent data is given relatively more weight in making the forecasting。
Double and triple exponential smoothing can be used to help with different
types of trend。 More sophisticated still are Holt’s and Brown’s linear exponential
smoothing and Box…Jenkins； named a。。er two statisticians of those
names； which applies autoregressive moving average models to find the
best fit of a time series。
Fortunately； all an MBA needs to know is that these and other statistical
forecasting methods exist。 The choice of which is the best forecasting technique
to use is usually down to trial and error。 Various so。。ware programs
will calculate the best…fi。。ing forecast by applying each technique to the
historic data you enter。 Then wait and see what actually happens and use the
technique that’s forecast as closest to the actual oute。 Professor Hossein
Arsham of the University of Baltimore （h。。p：//home。ubalt。edu/ntsbarsh/
Business…stat/otherapplets/ForecaSmo。htm#rmenu） provides a useful tool
that allows you to enter data and see how different forecasting techniques
perform。 Duke University’s Fuqua School of Business； consistently ranked
among the top 10 US business schools in every single functional area；
provides this helpful link （duke。edu/~rnau/411home。htm） to all its
lecture material on forecasting。
Causal relationships
O。。en； when looking at data sets it will be apparent that there is a relationship
between certain factors。 Look at Figure 11。3。 It is a chart showing the
monthly sales of barbeques and the average temperature in the preceding
month for the past eight months。
It’s not too hard to see that there appears to be； as we might expect； a
relationship between temperature and sales； in this case。 By drawing the
line that most accurately represents the slope； called the line of best fit； we
can have a useful tool for estimating what sales might be next month； given
the temperature that occurred this month （Figure 11。4）。
The example used is a simple one and the relationship obvious and
strong。 In real life there is likely to be much more data and it will be harder
to see if there is a relationship between the ‘independent variable’； in this
254 The Thirty…Day MBA
case temperature； and the ‘dependent variable’； sales volume。 Fortunately；
there is an algebraic formula known as ‘linear regression’ that will calculate
the line of best fit for you。
There are then a couple of calculations needed to test if the relationship
is strong （it can be strongly positive or even if strongly negative it will still
be useful for predictive purposes） and significant。 The tests are known as
R…squared and the Students t…test； and all an MBA needs to know is that
they exist and you can probably find the so。。ware to calculate them on your
puter already。 Otherwise you can use Web…Enabled Scientific Services
& Applications （wessa/slr。wasp） so。。ware； which covers almost
every type of statistical calculation。 The so。。ware is free online and provided
Figure 11。4 Sca。。er diagram – the line of best fit
Figure 11。3 Sca。。er diagram example
0
200
400
600
800
1000
1200
1400
1600
0 20 40 60 80 100
Temperature （F）
Sales units （ooo's）
0
200
400
600
800
1000
1200
1400
1600
0 20 40 60 80 100
Temperature （F）
Sales units （000's）
Quantitative and Qualitative Research and Analysis 255
through a joint research project with K。U。Leuven Association； a network of
13 institutions of higher education in Flanders。
For help in understanding these statistical techniques； read The Li。。le
Handbook of Statistical Practice by Gerard E Dallal of Tu。。s； available free
online （tu。。s。edu/~gdallal/LHSP。HTM）。 At Princeton’s website （h。。p：//
dss。princeton。edu/online_help/analysis/interpreting_regression。htm） you
can find a tutorial and lecture notes on the subject as taught to its Master of
International Business students。
QUALITATIVE RESEARCH AND ANALYSIS
Qualitative research is a well…entrenched academic tradition in sociology；
history； geography and anthropology； it is widely used in the medical
and political fields。 It has made much less of a mark in business； perhaps
because of its image as a so。。er； more ethereal discipline。 That situation is
changing with the growing realization that while quantitative research can
reveal what issues are important and even where they lie； it is of