The assignment was to:
In the write ups, I asked you to include a short summary of the article so that readers could make sense of your contribution without having the article at hand.
See how a math professor did the assignment.
Terrance Odean, a professor at the University of California-Davis, conducted a study proving that the stocks investors sold outperformed the ones that they held by 3.4 percent. He analyzed 10,000 accounts over a seven-year period ending in 1993. The continuous variable (the difference between the dollar amount yielded from the held stock and the sold stock) is dependent upon whether the market is up or down. Another continuous variable would be the risk involved concerning the different stocks. The 10,000 accounts could be broken down into high and low risk categories and classified by company. The stocks of specific companies that were held may have outperformed those sold, but when averaged, the percentage was in favor of the sold stock. In addition, stocks classified as `high risk' may have had a better outcome than the `low risk' ones, but not good enough to change the performance average of 3.4 percent (or vice-versa). In the study, the percentage was calculated only a year after the study ended. Since it only lasted until 1993, we don't know if the stocks that were sold have lowered or risen since then. It is possible that if we looked at those same 10,000 accounts in 1998, the stocks held may be worth more than the stocks sold in 1993.
The article is an adaptation from his book, "Tapped Out" and will be published next month.
SUMMARY: This article tackles the current issue of water stress and shortage and predicts future world needs in relation to clean water sources.
The first statistic in question is figure for the world?s population. Simon states with no reference that "the world?s population of 5.9 billion will double in the next 50 to 90 years, depending on whose estimates you accept." In the same paragraph, he claims that, per capita, water consumption is rising twice as fast as the world?s population. It is not clear how he accurately measured these variables, and it is obvious that the world population can never accurately be measured, much less predicted for the future. Simon then notes that 22 nations currently depend on their neighbors for water. The set of countries that he claims have water shortage is adequate for now, but could change depending on pollution or natural events that could skew the amount of water and the distance that must be traveled to reach it. The primary graph of the article contains a statistic that appears to be underestimated. Simon states that people under 'stress' have less than 1700 cubic meters available per person and people with ?scarcity? have less than 1000 cubic meters per person. Simon does not say if this water is nearby and what the conditions of the water are. The graph shows the world population, as of 1995, with 5% under stress and 3% under scarcity. He estimates that the world population in 2050 will be 9.4 billion; only 24% with stress and 18% with scarcity. Yet, he later says that by 2050, 4 billion people will be under severe water shortage which is nearly half of the projected population. Does "severe water shortage" not mean the same thing as 'stress' and 'scarcity.' These figures do not accurately correspond with the graph. Other questions to ask: How is this measured and how much is 1700/1000 cubic meters a day in terms of the amount of healthy water consumption. These figures, even if measured correctly would change over time because of population fluctuations and the amount of pollution affecting water sources. Overall, the article was lacking solid facts. Most of the statistics focused on things that may happen in the future which cannot truly be estimated and the statistics that were supposedly current appear questionable. The author does not cite references, nor does he explain the source of his data
In the article "Explaining Erratic Behavior" (US News and World Report: August 31, 1998), the variables are summarized in a graph at the bottom of the page. Each of the two variables represents the performance of two indexes of the New York Stock Exchange since January in terms of percent above "normal." Normal--in this case--is the level the stock market reached at the end of the first day of trading of 1998. One index that is measured is the Russell 2000 Index, a consortium of 2000 stocks. The other is the famous Dow Jones Industrial Average (DJIA), which is a measurement of an elite group of well-known, historically good-performing stocks. These particular variables were derived by monitoring the market's daily closing marks and converting the reading to a percentage above (or below) normal. The numbers were converted using this formula:
f(t) = ((x[t] - x[n]) / x[n]) * 100
where x[t] is the reading for each trading day and x[n] is the market's performance on the first day of trading. Multiplying by 100 gives the difference in terms of percentage. The graph shows the last reading given for the DJIA is +7.14% on August 21, 1998. This means that when the closing bell rang on Wall Street on August 21, the DJIA ended up at a value 7.14% higher than it did on the first trading day. The value for the Russell 2000 Index is -9.36%, which shows that this index ended at a value 9.36% lower than it opened on the first day. The graph supports the conclusion that the DJIA, a major stock group that only gages the performance of a few, strong stocks, can not be considered a good indicator of the overall performance of the stock market. The DJIA represents only a small cross section of stocks in the entire market, while the Russell 2000 monitors a larger sample. Therefore, the Russell 2000 Index (which is not doing well) provides more accurate evidence of the market's performance, especially in light of recent panics and crises.
This article deals with the risk of prostate cancer due to exposure to pesticides. Studies have shown that farmers that have been exposed pesticides and cadmium compounds seem to have an increased risk in developing cancer than men of similar age that have not been exposed to pesticides. The study used as a sample 20,025 Swedish men who have had exposure to pesticides. The study showed that of the 20,000 men in the sample, only 401 had actually developed prostate cancer. This small portion of the sample actually developing cancer demonstrates that cadmium may indeed pose an increased risk of cancer. To determine whether or not pesticides do actually pose an increased risk, a sample of similarly aged men who had not been exposed to pesticides could be used. The quantitative variables in this study include the length of exposure to pesticides, the amount of pesticides handled by each individual, and the composition of the chemicals used by the pesticides.
Scientists conducted a new study to test the theory that teens who play sports get better grades, but are more likely to use alcohol and drugs. The quantitative variable was the percentage of students who participated in sports and other activities and the percentage of students who also use drugs and alcohol out of a group of 1259 tenth graders. 46% of the girls and 67% of the boys played sports in the study. The variable varied depending on the activity, the sex of the student, and their drug and alcohol use. The students who played sports and participated in other extracurricular activities made better grades and were more likely to use drugs and alcohol. But the research couldn't identify the reasons and did not link athletes with other problem behaviors. The results do not seem reliable to me because there is no reasoning behind the scientists conclusion. The test could be circumstantial or the testing could be flawed.
The main focus of this article is to inform the public of the results of a new cancer finding technique called PCR. The data portion of these results were presented in the article in numeric form. I found this article to be very appropriate for this assignment since it contains two different instances where quantitative variables are used in order to make a point. Both of these cases are brought about as the result of scientific studies in the medical field. Quantitative variables can clearly be found in the statistic stating that using a sample of 178 children who appeared to be in remission after chemotherapy, the PCR test found that 42 percent of these children were still infected with traces of cancer. Upon follow up testing, 40 percent of the children showing traces of the disease suffered a relapse as compared to only 8 percent of those who tested ?cancer free.? In the final paragraph the article cites a different study which uses probabilities to make its point. The study states that while four-fifths of children diagnosed with acute lymphoblastic leukemia can be cured, only one-third of adults infected with the same form of cancer ever fully recover. This study is based on the cases of 3,000-4,000 people who are diagnosed with lymphoblastic leukemia each yeas. Overall this article makes excellent use of quantitative variables. Throughout this article numeric data is used to highlight the importance of these findings. This use of quantitative variables helps to emphasize the significance of catching this potentially fatal disease as early as possible, as well as helping to show the possibility of preventing relapses after treatments.
This article is about the rate of maternal deaths in the last 15 years. This rate is a quantitative variable. According to the article, there are 7-8 maternal deaths per 100,000 births in the United States. The maternal death rate varies from country to country and is used as a measure of the average health of each country. In some countries where overall health is not as good as it is in the United States, the rate is as high as 1,700 deaths per 100,000 births; in other countries it is about half that of the United States. The Centers for Disease Control and Prevention (CDC) found the number of maternal deaths for a given year by checking death certificates. However, the information is not necessarily always correct on a death certificate if it was not reported correctly. According to the CDC, half of the maternal deaths could be prevented.
Quantitative variables (variables to which a number can be assigned) can be found all around us. An example can be found in the article "Parents no longer rush to flush toddlers' diapers" form the August 25, 1998 edition of USA Today. Here the variable is the age at which toddlers are potty trained. According to the article, the age is moving up due to recent research indicating that slow and steady results in less health problems, such as bedwetting or chronic constipation, in the child's future. They list a study from "Pediatrics" conducted in 1997 that shows at what age toddlers in the sample were potty trained, with 97.7% being trained at 48 months. The article, however, does not list any study to back up its opinion that this is healthier. All the article lists is the opinion of T. Berry Brazelton, a "child-development expert" who, conveniently, works for Pampers, a diaper manufacturer. He supports the child-decided time to train, and he mentions how the company he works for is now making diapers to support this growing number of larger babies still in diapers. If the article wanted their opinion to be credible, more studies with variables such as the number of toddlers who had bedwetting problems and were trained at what age, or if they were forced into training. Listing one study with the ages they are trained is not enough to support Mr. Brazelton's seemingly biased opinion, nor is it enough to publish an article making suggestions to parents about how best to raise their child.
For the over two million Americans who suffer from rheumatoid arthritis, the future is looking brighter than ever as the testing of two new drugs, Enbrel and Arava, are being performed. Enbrel is a biologically engineered cell receptor which absorbs excess amounts of the substance, TNF, which causes most of the inflammation. Arava is a chemical that stops the overproduction of cells that cause inflammatory joints. Next month, the two drugs will be placed before the FDA for approval for general sale. In the tests done on Enbrel, two hundred and thirty-four rheumatoid patients underwent the treatment. Of the two hundred and thirty-four, sixty- two percent of the patients' conditions improved. In the tests done with Arava, forty-one percent of the four hundred and eighty patients' conditions improved. The main argument against these tests is the reader does not know how serious the conditions of the patients were. If the patients were suffering from severe cases, the results would be exceptional, but if the patients only had mild cases the percentages are really not that high. Another argument could be the tests did not encompass a large enough population, but I disagree with this. The total number of American patients is approximately two million. Based on this, the results of the experiments should be fairly accurate.
This article examines two continuous variables and their relationship in the Dow Jones recent trend of unpredictability. The first of these variables is in the form of a percentage point. This daily percentage is used to measure either a rise or decline in the stock market when compared to the previous day's number. The second variable, that of an overall gross number, directly relates to the first variable in that as the gross number rises, so rises the percentage point (likewise for a decline). A rise in the variables tends to signify a good day for the market, and a decline in the variables means a bad day. Investors rely heavily upon the fate of the variables, as a rise or decline in the variables determines how an investor will work with his/her stock holdings in the future. The variables can be understood in the following diagram: Let C stand for the variable. We compute the variable's value on a given day (x) as follows: C(x) = 100 (closing Dow on day x - closing Dow on day [x-1]) / closing Dow on day [x-1]. This would give you a percentage, which could then be compared to numbers from the previous day to determine if the Dow Jones had risen or fallen. The variables were primarily drawn into comparison to illustrate how of recent times the stock market has been very unpredictable. This was supported by showing that where one day an increase a percentage point would be seen, giving optimism to investors, the following day a decline would occur. Both variables tended to fluctuate frequently, still they were heavily drawn upon, as they determined the fate of an investor's stocks on the market.
Summary: This articles tells of a 7-year survey done that looked at HIV tests for 350,000 youths in the federal Job Corps program. This program provides job training to poor youths and high school dropouts. The results of the study placed women ages 16 to 21 at a higher risk, double that of the males, of contracting AIDS than men of the same age.
The non-discrete variable addressed in this article is the number of people per 1,000 in a certain age group of each sex who have contracted AIDS. Several factors are relevant to the outcome of the tests and the value of each variable in each population. Some such factors were age, sex, and race. Young black women had the highest infection rate out of all sample groups. The sample group contained 350,000 youths in the federal Jobs Corps program that had acquired HIV tests. While the size of this sample group seems to be large enough to attain an accurate result from the survey, the tested group might not accurately represent the entire population. Because all of the tested subjects were either poor or high school drop outs this possibly places them at a higher risk of contracting AIDS than the rest of the population. Because of this, this sample group is not an accurate representation of all youths. Also, the testing was done strictly in large urban areas. Because of the lack of variation in test subjects the results might be inaccurate. In order to correct this, the poll must include youths from all areas and classes. This would allow us to more accurately infer data about larger, National populations. The rate of AIDS in each test division is continuous because as other factors change, the rate of AIDS changes continuously and can be any percent of the population between zero and 100; this includes fractions. A variable such as sex is discrete because it will either be female or male.
The Wall Street Journal published an article,"Wonder Years", in the March 98 Classroom Edition, which explained how teenagers in the nineties differ from teenagers in the past. A poll conducted by the Rand Youth Poll supplemented the article. The poll used actual and estimated data to provide statistics that show the total amount of money spent by teenagers in year. The poll did this for each since 1953 to 1997. The quantitative variable discussed is the amount of money spent by all teenagers in a year. Another quantitative variable discussed is the total teenage population for each year. These two variables are combined on a chart that indicates a relationship between total teenage spending and total population. As the population rises teenage spending rises; however, this information is not the purpose of the statistic. The poll reports data about teenage spending without informing the reader of the methods used to accumulate the data. The poll's methods are unclear, which leaves the reader questioning the accuracy of the data. Some information is revealed, but not much. The money spent by teenagers comes from parents and jobs. The money could have been spent on anything a teenager might buy, which could be a pack of gum or a new car. No other information is revealed. Consequently, many questions arise. How many teens were polled? Were teens polled or were parents of teens polled? Was the poll telephoned, voluntary, randomly sampled, and were the questions biased? What was the margin or error and how confident is the Rand Youth Poll in the statistics? This lack of information leads to an inaccurate statistic, because many important questions are left unanswered. The average amount of money spent by teenagers lacks significance not only because the poll lacks important information about it's methods, but also because total teen spending is not important information. The poll may entertain an interested reader who enjoys meaningless statistics. The poll predicts that teenagers will set a new teenage spending record as we approach the year 2000, which may be true, even though the poll has not reveal it's method for the prediction.