46 Chrysalises for Cash The colorful butterfly symbolizes the notion of personal change. Increasing- ly, people are turning to butterflies to consecrate meaningful events such as birthdays, weddings, and funerals.To fill this need, a new industry was hatched. Suppliers of butterflies are closely monitored by governmental agencies to ensure that local environments are not subjected to the introduction of invasive species. In addition to following these regu- lations, butterfly suppliers need to ensure the quality and quantity of their product, while maintaining a profit. To that end, an individual supplier may hire a number of smaller independent contractors to hatch the varieties needed.These entrepreneurs are paid a small fee for each chrysalis delivered, with a 50 percent bonus added for each hatched healthy butter- fly. This fee structure provides little room for profit. Therefore, it is impor- tant that these small contractors deliver a high proportion of healthy butterflies that hatch at a fairly predictable rate. In Florida, one such entrepreneur specializes in harvesting the black swallowtail butterfly. In the southern United States, the black swallowtail has at least three broods annually. The female flutters through open fields seeking plants of the Apiaceae family, such as carrot and parsley, upon which to lay her eggs. The resulting larvae are dark brown with a small white saddle mark. As the larvae consume the leaves of their host plant, they increase in size, changing color to a vibrant green with intermittent stripes of yellow and black. Once a larva has eaten enough, it secures itself and sheds its skin, revealing an emerald chrysalis. During this resting phase, environmental factors such as temperature and humidity may affect the transformation process.Typically, the black swallowtail takes about a week to complete its metamorphosis and emerge from its cocoon. The transfor- mation occasionally results in a deformed butterfly. Deformities range from wings that will not fully open to missing limbs. The Florida contractor believes that there are differences in quality and hatch time among his broods. Not having taken a scientific approach to the problem, he relies on his memory of seasons past. It seems to him that late season butterflies hatch sooner and with a greater number of deformities than their early season counterparts. Additionally, he speculates that the type and nutritional value of the food consumed by the larva might con- tribute to any observed differences.This year he is committed to a more for- mal approach to his butterfly harvest. Since it takes two days to deliver the chrysalises from the contractor to the supplier, it is important that the butterflies do not emerge prematurely. It is equally important that the number of defective butterflies be mini- mized. With these two goals in mind, the contractor seeks the best combina- tion of food source, fertilizer, and brood season to maximize his profits. In order to examine the effects of these variables on hatch time and number of deformed butterflies, the entrepreneur designed the following experiment: Eight identical pots were filled with equal amounts of a particular soil mixture. The watering of all the pots and the plants contained within them was carefully monitored for consistency. Four pots were set outside during the early part of the brood season. Of these, two contained carrot plants, CASE STUDY SullStatCH01_Fpp2-49 11/20/02 10:12 AM Page 46
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46
Chrysalises for Cash
The colorful butterfly symbolizes the notion of personal change. Increasing-ly, people are turning to butterflies to consecrate meaningful events such
as birthdays, weddings, and funerals. To fill this need, a new industry washatched.
Suppliers of butterflies are closely monitored by governmentalagencies to ensure that local environments are not subjected to the
introduction of invasive species. In addition to following these regu-lations, butterfly suppliers need to ensure the quality and quantity
of their product, while maintaining a profit. To that end, an individualsupplier may hire a number of smaller independent contractors to hatch thevarieties needed.These entrepreneurs are paid a small fee for each chrysalisdelivered, with a 50 percent bonus added for each hatched healthy butter-fly. This fee structure provides little room for profit. Therefore, it is impor-tant that these small contractors deliver a high proportion of healthybutterflies that hatch at a fairly predictable rate.
In Florida, one such entrepreneur specializes in harvesting the blackswallowtail butterfly. In the southern United States, the black swallowtailhas at least three broods annually. The female flutters through open fieldsseeking plants of the Apiaceae family, such as carrot and parsley, uponwhich to lay her eggs. The resulting larvae are dark brown with a smallwhite saddle mark. As the larvae consume the leaves of their host plant,they increase in size, changing color to a vibrant green with intermittentstripes of yellow and black. Once a larva has eaten enough, it secures itselfand sheds its skin, revealing an emerald chrysalis. During this resting phase,environmental factors such as temperature and humidity may affect thetransformation process. Typically, the black swallowtail takes about a weekto complete its metamorphosis and emerge from its cocoon. The transfor-mation occasionally results in a deformed butterfly. Deformities range fromwings that will not fully open to missing limbs.
The Florida contractor believes that there are differences in quality andhatch time among his broods. Not having taken a scientific approach to theproblem, he relies on his memory of seasons past. It seems to him that lateseason butterflies hatch sooner and with a greater number of deformitiesthan their early season counterparts. Additionally, he speculates that thetype and nutritional value of the food consumed by the larva might con-tribute to any observed differences.This year he is committed to a more for-mal approach to his butterfly harvest.
Since it takes two days to deliver the chrysalises from the contractor tothe supplier, it is important that the butterflies do not emerge prematurely.It is equally important that the number of defective butterflies be mini-mized.With these two goals in mind, the contractor seeks the best combina-tion of food source, fertilizer, and brood season to maximize his profits. Inorder to examine the effects of these variables on hatch time and number ofdeformed butterflies, the entrepreneur designed the following experiment:
Eight identical pots were filled with equal amounts of a particular soilmixture. The watering of all the pots and the plants contained within themwas carefully monitored for consistency. Four pots were set outside duringthe early part of the brood season. Of these, two contained carrot plants,C
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while the remaining pair grew parsley. For the carrot pair, one pot was fed afixed amount of liquid fertilizer, while the other pot was fed a nutritionallysimilar amount of solid fertilizer. The two pots containing parsley were sim-ilarly fertilized. All four pots were placed next to each other to ensure simi-lar exposures to environmental conditions such as temperature and solarradiation. Five black swallowtail larvae of similar age were placed into eachcontainer.The larvae were allowed to mature and form a chrysalis.The timefrom chrysalis formation until emergence was reported to the nearest day.The occurrence of any defects was also noted. The same procedure was fol-lowed with the four pots that were placed outdoors during the late broodseason.
Write a report describing the experimental goals and design for the en-trepreneur’s experiment. Follow the procedure outlined in the section titledSteps in Conducting an Experiment (pp. 36–37). The fifth step (collect andprocess the data) of this procedure is provided in the following table andshould be included in your report.
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Number Hatch TimeSeason Food Fertilizer Deformed (Days)
Early Parsley Solid 0 6,6,7,7,7
Early Parsley Liquid 0 6,7,7,8,8
Early Carrot Solid 1 3,6,6,7,8
Early Carrot Liquid 0 6,6,7,8,8
Late Parsley Solid 2 2,3,4,4,5
Late Parsley Liquid 1 2,3,4,5,5
Late Carrot Solid 2 3,3,3,4,5
Late Carrot Liquid 0 2,4,4,4,5
Florida Black Swallowtail Chrysalis Experiment Data
In your report, provide a general descriptive analysis of these data. Besure to include recommendation for the combination of season, foodsource, and type of fertilizer that results in the least amount of deformedbutterflies while achieving a lengthy hatch time.
Conclude your report with recommendations for further experiments.For each proposed experiment, be sure to
1. State the problem to be solved and define the response variables.2. Define the predictor variables that affect the response variables.3. State the number of experimental units.4. State the level of each predictor variable.
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What Movie Should I Go To?
One of the most difficult tasks of surveying is phrasing questions so thatthey are not misunderstood. In addition, they must be phrased so that theresearcher obtains answers that allow for meaningful analysis. The purposeof this exercise is to create a questionnaire that can be used to make an in-formed decision about whether to attend a certain movie. Select a moviethat you wish to see. If the movie is still in theaters, make sure that it hasbeen released for at least a couple of weeks so that it is likely that a numberof people have seen it. Design a questionnaire that would be filled out bythe individuals that have seen the movie.You may wish to include questionsregarding demographics of the respondents first (such as age, gender, levelof education, and so on). Ask as many questions as you feel would be nec-essary to obtain an opinion regarding the movie. The questions can be openor closed. Administer the survey to at least 20 randomly selected peoplewho have seen the movie. While administering the survey, keep track ofthose individuals who have not seen the movie. In particular, keep track oftheir demographic information. After administering the survey, summarizeyour findings. On the basis of the survey results, do you think that you willenjoy the movie? Why? Now see the movie. Did you like it? Did the surveyaccurately predict whether you would enjoy the movie? Now answer thefollowing questions:
(a) What sampling method did you use? Why? Did you have a frame forthe population?
(b) Did you have any problems with respondents misinterpreting yourquestions? How could this issue have been resolved?
(c) What role did the demographics of the respondent have in formingyour opinion? Why?
(d) Did the demographics of individuals who did not see the movie play arole while you were forming your opinion regarding the movie?
(e) Look up a review of the movie by a professional movie critic. Did themovie critic’s opinion agree with yours? What might account for thesimilarities or differences in your opinions?
(f) Describe the problems that you had in administering the survey. If youhad to do this survey over again, would you change anything? Why?
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Emotional “Aspirin”
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Americans have a long history of altering theirmoods—with chemicals ranging from alcohol and illic-it drugs to prescription medications, such as diazepam(Valium) for anxiety and fluoxetine (Prozac) for de-pression. Today there’s a new trend: the over-the-counter availability of apparently effective moodmodifiers in the form of herbs and other so-called di-etary supplements.
One problem is that many people who are treatingthemselves with these remedies may be sufficientlyanxious or depressed to require professional care andmonitoring. Self-treatment can be dangerous, particu-larly with depression, which causes some 20,000 re-ported suicides a year in the United States. Anothermajor pitfall is that dietary supplements are largelyunregulated by the government, so consumers have al-most no protection against substandard preparations.
To help consumers and doctors, Consumer Re-ports tested the amounts of key ingredients in repre-sentative brands of several major mood-changing pills(December 2000). To avoid potential bias, we testedsamples from different lots of the pills using a random-ized statistical design. The following table contains asubset of the data from this study:
Each of these pills has a label claim of 200 mg ofSAM-E. The column labeled “Random Code” con-tains a set of 3-digit random codes that were used sothat the laboratory did not know which manufacturerwas being tested. The column labeled “Mg SAM-E”contains the amount of SAM-E measured by the labo-ratory.
(a) Why is it important to label the pills with randomcodes?
(b) Why is it important to randomize the order inwhich the pills are tested instead of testing all ofbrand A first, followed by all of brand B, and soon?
(c) Sort the data by brand. Does it appear as if each ofthe brands are meeting their label claims?
(d) Design an experiment that follows the steps pre-sented in order to conduct an experiment to an-swer the following research question: “Is there adifference in the amount of SAM-E contained inbrands A, B, C, and D?”
Note to Readers: In many cases, our test protocol and analyticalmethods are more complicated than described in these examples.The data and discussions have been modified to make the materialmore appropriate for the audience.
Run Random Order Brand Code Mg SAM-E
1 B 461 238.9
2 D 992 219.2
3 C 962 227.1
4 A 305 231.2
5 B 835 263.7
6 D 717 251.1
7 A 206 232.9
8 D 649 192.8
9 C 132 213.4
10 B 923 224.6
11 A 823 261.1
12 C 515 207.8
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