Forecasting Exchange Rates 7
Solution to Supplemental Case: Whaler Publishing Co.
1. The first step is to measure the standard deviation of the percentage change in each exchange rate,
which can most easily be done with a spreadsheet. This information can then be used along with
today’s spot exchange rate to derive the confidence intervals for each exchange rate.
Approximate 68 Percent 95 Percent
Standard Confidence Confidence
Currency Deviation Interval Interval
Australian $ 9.59% $.6935 to $.8407 $.6200 to $.9142
Canadian $ 5.10 $.8185 to $.9065 $.7745 to $.9505
New Zealand $ 12.03 $.5265 to $.6705 $.4545 to $.7425
British pound 16.40 $1.6203 to $2.2560 $1.3024 to $2.5739
Using the intervals described above and the number of foreign currency units to be received from
each country, the range of forecasted U.S. dollar revenues (in thousands) from each country is
disclosed below:
68 Percent 95 Percent
Confidence Confidence
Currency Interval Interval
Australian $ $26,353 to $31,946 $23,560 to $34,739
Canadian $ $28,647 to $31,727 $27,107 to $33,267
New Zealand $ $17,374 to $22,126 $14,998 to $24,502
British pound $55,090 to $76,704 $44,282 to $87,512
The numbers here may differ slightly from those the students compute due to rounding. The standard
deviations estimated above suggest that the Canadian dollar is the most stable currency so the U.S.
dollar revenues coming from Canada are more predictable. Conversely, the standard deviation of the
British pound has been most volatile, so that the U.S. dollar revenues coming from the United
Kingdom are less predictable. The above comparison of predictability of U.S. dollar revenues from
various countries assumes that the foreign currency revenues in each country is known. In other
words, the reason for the uncertainty in dollar revenues is the exchange rate, not the demand for
textbooks by each given country.
Notice that the estimates were not pooled in any way to derive a confidence interval about the overall
dollar revenues. This would require an assumption that each exchange rate moves independently of
the others. If some of these currencies were positively correlated, such an assumption would cause
one to underestimate the dispersion in the confidence interval when combining estimates from
individual countries. If time permits, you may wish to challenge the students by asking them whether
combining the individual country results would be appropriate. The supplemental case in the
following chapter focuses on this issue and is an extension of this case.
Small Business Dilemma
Exchange Rate Forecasting by the Sports Exports Company
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