Researchers at Boston’s Children’s Hospital and Harvard Medical School analyzed records of breast cancer screening and diagnostic evaluations (National Expenditure for False-Positive Mammograms and Breast Cancer Overdiagnoses Estimated at $4 Billion a Year,” Health Affairs [2015]: 576–583). Discussing the downsides of the screening process, the article states that the rate of false-positives is higher than previously thought, and that false-positives lead to unnecessary medical follow-up that can be costly.
Suppose that screening is used to decide between a null hypothesis of
H0: no cancer is present
and an alternative hypothesis of
Ha: cancer is present.
(Although these are not hypotheses about a population characteristic, this exercise illustrates the definitions of Type I and Type II errors.) (Hint: See Example 10.6.)
- a. Would a false-positive (thinking that cancer is present when in fact it is not) be a Type I error or a Type II error?
- b. Describe a Type I error in the context of this problem, and discuss the possible consequences of making a Type I error.
- c. Describe a Type II error in the context of this problem, and discuss the possible consequences of making a Type II error.
- d. Which type of error are the researchers concerned about when they say that false-positives lead to unnecessary medical follow-up? Explain why it would be reasonable to use a small significance level.
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Chapter 10 Solutions
Introduction To Statistics And Data Analysis
- In a study conducted in the Science Department of Faculty of Science, Technology and Human Development in a University; the researcher examined the influence of the drug succinylcholine on the circulation levels of androgens in the blood. Blood samples from wild, free-ranging deer were obtained via the jugular vein immediately after an intramuscular injection of succinylcholine using darts and a capture gun. Deer were bled again approximately 30 minutes after the injection and then released. The level of androgens at time of capture and 30 minutes later, measured in nanograms per milliliter (ng/ml), for 15 deers as in Table Q1. Assuming that the populations of androgen at time of injection and 30 minutes later are normally distributed:i) Find the average and standard deviation of this studyii)Determine the critical region of this problem.iii) Test at the 0.05 level of significance whether the androgen concentrations are altered after 30 minutes of restraint.arrow_forwardDoes posting calorie content for menu items affectpeople’s choices in fast-food restaurants? According to results obtained by Elbel, Gyamfi, and Kersh(2011), the answer is no. The researchers monitoredthe calorie content of food purchases for children andadolescents in four large fast-food chains before andafter mandatory labeling began in New York City. Although most of the adolescents reported noticing thecalorie labels, apparently the labels had no effect ontheir choices. Data similar to the results obtained showan average of M = 786 calories per meal with s =85 for n =100 children and adolescents before thelabeling, compared to an average of M = 772 calorieswith s = 91 for a similar sample of n = 100 after themandatory posting.a. Use a two-tailed test with a = .05 to determinewhether the mean number of calories after theposting is significantly different than before caloriecontent was posted.b. Calculate r2to measure effect size for the mean difference.arrow_forwardRecently, the Shine research clinic published a report stating that the regular application of a very popular sunscreen lotion NoHelios might cause some forms of skin cancer. The manufacturer of NoHelios issued an energetic counterstatement asserting that the Shine clinic's conclusions were statistically inconsistent. Wellbeing pharmacy chain has been selling NoHelios lotion for a long time. The market research department of Wellbeing wants to see what is currently happening with NoHelios lotion demand. The members of a random sample of customers were asked about their willingness to use NoHelios before and after the publication of Shine clinic's report. The answers were provided in form of a score from 0 to 10 (higher score means more willingness). Results for five customers are shown in the following table. The "before" score is matched to the "after" score, and the difference should be calculated. Suppose that it is known that such differences have approximately bell-shaped…arrow_forward
- Red Wine and Weight LossResveratrol, a compound in grapes and red wine, has been shown to promote weight loss in rodents and now in a primate.1 Lemurs fed a resveratrol supplement for four weeks had decreased food intake, increased metabolic rate, and a reduction in seasonal body-mass gain compared to a control group. Suppose a hypothetical study is done for a different primate species, with one group given a resveratrol supplement and the other group given a placebo. We wish to see if there is evidence that resveratrol increases the mean metabolism rate for this species. (This exercise presents hypothetical data. We will see the results from the actual study later in this chapter.) (a) State the null and alternative hypotheses.Let group 1 be the species taking a resveratrol supplement and let group 2 be the species taking a placebo.arrow_forwardCardiovascular disease is a major cause of death and illness worldwide, with high blood pressure and high LDL cholesterol both being established risk factors. Because most cardiovascular events occur in persons with average risk and no previous cardiovascular disease history, the present research examined the simultaneous use of both blood pressure‑reducing drugs and cholesterol‑reducing drugs on this population rather than focus on only those at high risk. Subjects included men at least 55 years old and women at least 65 years old without cardiovascular disease who had at least one additional risk factor besides age, such as recent or current smoking, hypertension, or family history of premature coronary heart disease. Those with current cardiovascular disease were excluded from the study. Subjects were randomly assigned to the treatment (cholesterol‑ and blood pressure‑reducing drugs) or a placebo, and the number suffering the primary outcome of a fatal cardiovascular event or a…arrow_forwardSince its removal from the banned substances list in 2004 by the World Anti-Doping Agency,caffeine has been used by athletes with the expectancy that it enhances their workout andperformance. However, few studies look at the role caffeine plays in sedentary females.Researchers at the University of Western Australia conducted a test in which they determined therate of energy expenditure (kilojoules) on 10 healthy, sedentary females who were nonregularcaffeine users. Each female was randomly assigned either a placebo or caffeine pill (6mg/kg) 60minutes prior to exercise. The subject rode an exercise bike for 15 minutes at 65% of theirmaximum heart rate, and the energy expenditure was measured. The process was repeated on aseparate day for the remaining treatment. The mean difference in energy expenditure (caffeine –placebo) was 18kJ with a standard deviation of 19kJ. If we assume that the differences follow anormal distribution can it be concluded that that caffeine appears to increase…arrow_forward
- The National Institute of Mental Health published an article stating that in any two-year period, approximately 10.5percent of American adults suffer from depression or a depressive illness. Suppose that in a survey of 150 people in a certain town, eight of them suffered from depression or a depressive illness. If you were conducting a hypothesis test to determine if the true proportion of people in that town suffering from depression or a depressive illness is lower than the percent in the general adult American population, what would the null and alternative hypotheses be?arrow_forwardA consumer advocacy group wanted to study whether different airline carriers differed in terms of their delayed flights. In particular, the researchers were interested in the relationship between p1, the proportion of Alpha Airlines flights that were delayed at least 15 minutes, and p2, the proportion of Beta Airlines flights that were delayed at least 15 minutes. A random sample of 1,000 Alpha flights and a separate random sample of 1,000 Beta flights found that 67 of the Alpha fights and 160 of the Beta flights were delayed at least 15 minutes. The conditions for inference were checked and verified. Does this set of samples provide strong evidence that Alpha Airlines has a smaller proportion of flights that are delayed at least 15 minutes than Beta Airlines, at the α = 0.05 significance level? Find the z-table here. A. The test statistic is z = –6.56 and the P-value ≈ 0. Since the P-value ≈ 0 < 0.05, there is not sufficient evidence that Alpha Airlines has fewer delayed…arrow_forwardThe authors of the article "Adjuvant Radiotherapy and Chemotherapy in Node-Positive Premenopausal Women with Breast Cancer"† reported on the results of an experiment designed to compare treating cancer patients with chemotherapy only to treatment with a combination of chemotherapy and radiation. Of the 154 individuals who received the chemotherapy-only treatment, 76 survived at least 15 years, whereas 98 of the 164 patients who received the hybrid treatment survived at least that long. With p1 denoting the proportion of all such women who, when treated with just chemotherapy, survive at least 15 years and p2 denoting the analogous proportion for the hybrid treatment, p̂1 = (rounded to three decimal places) and p̂2 = (rounded to three decimal places). A confidence interval for the difference between proportions based on the traditional formula with a confidence level of approximately 99% is 0.494 − 0.598 ± (2.58) (0.494)(0.506) 154 + (0.598)(0.402) 164…arrow_forward
- Suppose a researcher is interested inthe effectiveness in a new childhood exercise program implemented in a SRS of schools across a particular county. In order to test the hypothesis that the new program decreases BMI (Kg/m2), the researcher takes a SRS of children from schools where the program is employed and a SRS from schools that do not employ the program and compares the results. Assume the following table represents the SRSs of students and their BMIs. Student intervention group BMI (kg/m2) Student control group BMI (kg/m2) A 18.6 A 21.6 B 18.2 B 18.9 C 19.5 C 19.4 D 18.9 D 22.6 E 24.1 F 23.6 A) Assuming that all the necessary conditions are met (normality, independence, etc.) carry out the appropriate statistical test to determine if the new exercise program is effective. Use an alpha level of 0.05. Do not assume equal variances.B) Construct a 95% confidence interval about your estimate for the average difference in BMI between the groups.arrow_forwardA researcher conducted a medical study to investigate whether taking a low-dose aspirin reduces the chance of developing colon cancer. As part of the study, 1,000 adult volunteers were randomly assigned to one of two groups. Half of the volunteers were assigned to the experimental group that took a low-dose aspirin each day, and the other half were assigned to the control group that took a placebo each day. At the end of six years, 15 of the people who took the low-dose aspirin had developed colon cancer and 26 of the people who took the placebo had developed colon cancer. At the significance level α = 0.05, do the data provide convincing statistical evidence that taking a low-dose aspirin each day would reduce the chance of developing colon cancer among all people similar to the volunteers?arrow_forwardChocolate contains caffeine and an endogenous cannabinoid, as well as a chemical thatmodulates serotonin production; but is it an aphrodisiac, as the Mayans and Aztecs believed?Suppose you conduct a study which measures sex drive in a group of 20 women, after eating 8ounces of chocolate. Given that you have available data from the Kinsey Institute (IndianaUniversity) about the general sex drive for women of the same demographic as in your study, youdecide to compare your group to this population estimate.If testing hypotheses about the effects of chocolate on sex drive, it would be most appropriate tocalculate a ...1)Paired sampled t2)Z-test3)Independent-samples t-test 4)One- sample t-testarrow_forward
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