INVESTIGATION: Does Vitamin C improve your health? | 137 INVESTIGATION: DOES VITAMIN C IMPROVE YOUR HEALTH? In 1970 Linus Pauling, a well-known chemist and Nobel Prize winning scientist, published Vitamin C and the Common Cold (1970), creating a great deal of public and scientific interest In short, Pauling argued that taking Vitamin C would reduce one's risk of the common cold This book almost singlehandedly made Vitamin Cone of the most widely used dietary supple- ments, a status it retains to this day (Nutritional Supplement Review, 2069). Subsequent to the publishing of his book, Pauling wrote a paper that appeared in the Proceedings of the National Academy of Sciences in 1971. In this paper he describes a study conducted by a physician in Basel, Switzerland, in the early 1960s. Here is an excerpt from the paper explaining the study design The study was carried out in a ski resort with 279 skiers during two periods of 5-7 days, The conditions were much that the incidence of colds diering these short periods was large enough (about 20%%) to permit results with statistical significance to be obtained. The subjects were roughly of the same age and had similar nutrition during the period of study The investiga- Hon was double-blind, with neither the participants nor the physicians having any knowl- edge about the distribution of the ascorbic acid tablets (1000 my) and the placeba tablets. The tablets were distribuded every morning and taken by the subjects under observation, so that the possibility of interchange of tablets was eliminated. The subjects were examined daily for symptoms of colds and other infections, The records were largely on the basis of subjective symptoms, partially supported by objective abservations (measurement of body temperature inspection of the respiratory organs, auscultation of the lungs, and so on) Persons who showed cold symptoms on the first day were excluded from the investigation After the completion of the investigation, a completely independent group of pro- fessional people was provided with the identification manbers for the ascorbic acid tablets and placebe tablets, and this group performed the statistical evaluation of the observations Although not stated explicitly in the paragraph above, the participants were randomly assigned to take ascorbic acid tablets or the placebo. STEP 1: Ask a research question. 1. State the research question. To enter special characters and STEP 2: Design a study and collect data. formatting, use "Curl+E in Windows and "Cind + E" in 2. Is this study an experiment or an observational study? How are you deciding! Mac. 3. What are the observational/experimental units? To enter special characters and formatting use "Curl+E in 4. What are the variables that are measured/recorded on each unit! Windows and "Cad . E" in Mac Print Reset 138 CHAPTER S Comparing Two Proportions 5. Describe the parameters of interest in words. ( You can use the symbol x to represent there parameters) To enter special characters and formatting use 'Cul+E in Windows and "Cand + B in 6. State the null and alternative hypotheses for a test of significance to see whether this experiment provides statistically significant evidence that Vitamin C prevented colds in the aklers Use a one-sided test To enter special characters and formatting. use "Chri4E in Windows and "Cod + E in Mac 7. Of the 139 skiers assigned to take Vitamin C. 17 developed a cold. Of the 140 skiers as- signed to take a placebo, 31 developed a cold, Fill in the 2 X 2 table provided. Vitamin C Placebo Total No cold Cold Total 8. Incidence is the term used to describe the percent of the sample who onset with an illness over a certain time period. la this case, the incidence rates are the same as the conditional proportions. Find the incidence rates for individuals who received Vitamin C and those who received the placebe To enter special characters and formalting, use Curl,E in Windows and "Cind + E in Mac STEP 3: Explore the data. . What is the difference in incidence rates in the two groups. Before doing a test of Significance, comment on whether you think the is evidence that Vitamin C prevents colds To enter special characters and