The paper “Effect of a Nutritional Supplement on Hair Loss in Women” (Journal of Cosmetic Dermatology [2015]: 76-82) describes an experiment to see if a dietary supplement consisting of Omega 3, Omega 6, and antioxidants could reduce hair loss in women with stage 1 hair loss. One hundred twenty women volunteered to participate in the study and were randomly assigned to either the supplement group or a control group. The women in the supplement group took the supplement for 6 months. Photos of the top of the head were taken of all the women at the beginning of the study and 6 months later at the end of the study. The two photos of each woman were evaluated by an independent expert who visually determined the change in hair density. The expert who determined the change in hair density did not know which of the women had taken the supplement.
- a. Evaluate this experimental design. Do you think this is a good design or a poor design, and why?
- b. If you were designing such a study, what, if anything, would you propose to do differently?
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Chapter 2 Solutions
Introduction To Statistics And Data Analysis
- Side effects of Avandia - Rosiglitazone is the active ingredient in the controversial type 2 diabetes medicine Avandia and has been linked to an increased risk of serious cardiovascular problems such as stroke, heart failure, and death. A common alternative treatment is pioglitazone, the active ingredient in a diabetes medicine called Actos. In a nationwide retrospective observational study of 227,571 Medicare beneficiaries aged 65 years or older, it was found that 2,593 of the 67,593 patients using rosiglitazone and 5,386 of the 159,978 using pioglitazone had serious cardiovascular problems. The data is summarized in the contingency table below. Cardiovascular problems Yes No Total Rosiglitazone 2,593 65,000 67,593 Pioglitazone 5,386 154,592 159,978 Total 7,979 219,592 227,571 1. What proportion of all patients had cardiovascular problems? Round your answer to four decimal places. 2. What is the difference in proportion of patients with cardiovascular problems between the…arrow_forwardVitamin E and the Risk of Prostate Cancer: Klien et al (2011) conducted the following study to determine the effect of vitamin E and selenium treatment on the risk of developing prostate cancer in healthy men. A total of 34,887 men from different study sites in the United States, Canada, and Puerto Rico were randomly selected. To be eligible to participate, the men had to take a rectal examination that showed he was not suspicious of having prostate cancer and be aged 50 years or older for black men and 55 years or older for all others. Each man was randomly assigned to receive one of four treatments: selenium, vitamin E, selenium and vitamin E together, or a placebo. The men were followed up after 8 years to see if they had developed prostate cancer or not. The main question of interest is to determine if the risk of developing prostate cancer differs by the treatment taken. The data are summarized in the table below: No Prostate Cancer Prostate Cancer Total Selenium 8,752 8,737 8,702…arrow_forwardTen adult males between the ages of 30 and 40 participated in a study to evaluate the effect of a specific health regimen involving diet and exercise on the blood cholesterol. Five were randomly selected to be a control group, and five others were assigned to take part in the regimen as the treatment group for a period of 6 months. The following data show the reduction in cholesterol experienced for the time period for the 10 subjects: Control group: 7, 3, -4, 14, 2 Treatment group: -6, 5, 9, 4, 4 Compute the sample mean and standard deviation for Control Group. Select one: O A. 4.4, 44.3 О В. 4.4, 6.66 о С. 3.2, 5.54 O D. 3.2, 30.7arrow_forward
- Dark Chocolate for Good Health A study¹ examines chocolate's effects on blood vessel function in healthy people. In the randomized, double-blind, placebo-controlled study, 11 people received 46 grams (1.6 ounces) of dark chocolate (which is naturally flavonoid-rich) every day for two weeks, while a control group of 10 people received a placebo consisting of dark chocolate with low flavonoid content. Participants had their vascular health measured (by means of flow-mediated dilation) before and after the two-week study. The increase over the two-week period was measured, with larger numbers indicating greater vascular health. For the group getting the good dark chocolate, the mean increase was 1.3 with a standard deviation of 2.32, while the control group had a mean change of -0.96 with a standard deviation of 1.58. ¹Engler, M., et. al., "Flavonoid-rich dark chocolate improves endothelial function and increases plasma epicatechin concentrations in healthy adults," Journal of the…arrow_forwardThe Joint Commission on Accreditation of Healthcare Organizations mandated that hospitals ban smoking by 1994. To study the effects of this ban on smoking behaviors, subjects were randomly selected from two different populations: those from hospitals with the ban and those from hospitals without the ban. Investigators were interested in determining if this smoking ban had any impact on the proportion of smokers employed at each hospital that then quit smoking. Among 843 smoking employees of hospitals with the smoking ban, 56 quit smoking during the study period. Among 703 smoking employees from workplaces without the smoking ban, 27 quit smoking during the study period. Below is the Stata output that was run to determine if there was a statistically significant difference between these two proportions at the α=0.05 level. A. What is the estimate of the proportion of smokers from the hospitals that implemented the ban that quit smoking (the blank labeled "C" in the above output)?…arrow_forwardAngioplasty is a medical procedure in which an obstructed blood vessel is widened. In some cases, a wire mesh tube, called a stent, is placed in the vessel to help it remain open. The article “Long-term Outcomes of Patients Receiving Drug-eluting Stents” (A. Philpott, D. Southern, et al., Canadian Medical Association Journal, 2009:167–174) presents the results of a study comparing the effectiveness of a bare metal stent with one that that has been coated with a drug designed to prevent reblocking of the vessel. A total of 5320 patients received bare metal stents, and of these, 841 needed treatment for reblocking within a year. A total of 1120 received drug coated stents, and 134 of them required treatment within a year. a) Find a 98% confidence interval for the differences between the proportions for drug coated stents and bare metal stents. b) Suppose that additional patients are to be treated in order to increase the precision of the confidence interval. Three sampling plans are…arrow_forward
- Do cell phones increase drivers' reaction times while driving? A 2003 American Journal of Health Education study investigated the effects of cell phone use on reaction time. In the study, 60 participants were randomly selected and placed into one of two groups: the cell phone group or the control group. Those in the control group participated in the experiment with no distractions, whereas those in the cell phone group had access to text documents on a cell phone. Participants in each group were then asked to take a computerized reaction time test. Researchers then recorded each subject's reaction time in seconds. The table shows the results of the experiment. Group Populationmean Samplesize Samplemean Sample standarddeviation Phone up n=30 x¯P=0.546 sx=0.213 Control uc n=30 x¯C=0.356 sx=0.245 df=56.900 Suppose the researchers wish to examine at a significance level of alpha=0.05 if the mean reaction time for phone users is larger than the mean reaction time for the…arrow_forwardThe Joint Commission on Accreditation of Healthcare Organizations mandated that hospitals ban smoking by 1994. To study the effects of this ban on smoking behaviors, subjects were randomly selected from two different populations: those from hospitals with the ban and those from hospitals without the ban. Investigators were interested in determining if this smoking ban had any impact on the proportion of smokers employed at each hospital that then quit smoking. Let px be the proportion of smokers from hospitals that implemented the ban who quit smoking during the study period. Let py be the proportions of smokers from hospitals without the ban who quit smoking during the study period. Please select the appropriate hypotheses. H0: px = 0.50 HA: px ≠ 0.50 H0: px-py ≥ 0 HA: px-py H0: px-py ≤ 0 HA: px-py > 0 H0: px-py = 0 HA: px-py ≠ 0arrow_forward"Does ginkgo improve memory?" The law allows marketers of herbs and other natural substances to make health claims that are not supported by evidence. Brands of ginkgo extract claim to "improve memory and concentration." A randomized experiment found some statistically significant evidence for such effects. The subjects were 250 healthy volunteers over 65 years old. They were randomly assigned to take ginkgo or a placebo pill (a dummy pill that looks and tastes the same). All the subjects took a battery of tests for learning and memory before treatment started and again after six weeks. a). The article said the study was double-blind. What does this mean in the context of this study? Be very specific on who's being blinded and explain why they should be blinded. b). You suspect physical fitness and mental fitness go hand-in-hand. Create a flow chart to describe a design for an experiment to include the confounding variable physical fitness. Be very specific in your design. Include all…arrow_forward
- Suppose a study investigated the effects of vitamin A, vitamin C, and omega-3 fatty acids supplements on improving eye health and vision. 300 adults volunteered to take part in the study. In the study, participants were randomly assigned to one of 3 different levels of Vitamin A (Level A, Level B, or Level C) and randomly assigned to one of 2 different levels of Vitamin C (Level 1 or Level 2) and randomly assigned to one of 2 different levels of omega-3 fatty acid (Level I or Level II). a. Identify the subjects of the study. b. Identify the factor(s) for the study and the number of treatment level(s) for each factor. c. How many different treatment groups are there in this study?arrow_forwardKava is a beverage or extract that is made from Piper methysticum, a plant native to the western Pacific islands. Suppose that, in a randomized comparative experiment to determine if taking kava daily can reduce insomnia, a group of participants with insomnia were randomly assigned to take kava (treatment group) or a placebo (control group). After six weeks, the participants were interviewed to see if they experienced a decrease in insomnia. The table shows the results from the sample. The counts are the number of people in each group who experienced a decrease in insomnia. Group Description Population proportion Sample size Sample count Sample proportion 1 Treatment (kava) P1 n₁ = 402 x1 = 213 P₁ = 0.5299 2 Control (placebo) P2 n₂ = 521 x₂ = 121 P2 = 0.2322 Compute the standard error estimate, SE, of the difference in the sample proportions. Give your answer to at least four decimal places. 0.0438 SE = Incorrect Determine the value of the two-sample z-statistic for the difference in…arrow_forwardAs men age, their testosterone levels gradually decrease. This may cause a reduction in energy, an increase in fat, and other undesirable changes. Do testosterone supplements reverse some of these effects? A study in the Netherlands assigned 237 men aged 60 to 80 with low or low-normal testosterone levels to either a testosterone supplement or a placebo. Why is it necessary to include a control group in this experiment? Every experiment needs a control group in order to make proper comparisons between treatments. A control group is necessary to balance the effects of other variables among the treatment groups. A control group is necessary so any differences in the effects of the treatments can be distinguished from chance differences between the groups. A control group helps avoid confounding and reduces variability in the response variable. A control group is used to provide a baseline for comparing the effects of other treatments.arrow_forward
- Holt Mcdougal Larson Pre-algebra: Student Edition...AlgebraISBN:9780547587776Author:HOLT MCDOUGALPublisher:HOLT MCDOUGAL