Concept explainers
Salmonella in produce. Salmonella infection is the most common type of bacterial food-borne illness in the United States. How prevalent is salmonella in produce grown in the major agricultural region of Monterey, California? Researchers from the U S Department of Agnculture (USDA) conducted tests for salmonella in produce grown in the region and published their results in Applied and Environmental Microbiology (April 2011). In a sample of 252 cultures obtained from water used to Irrigate the region. 18 tested positive for salmonella In an independent sample of 476 cultures obtained from the region’s wildlife (e.g., birds), 20 tested positive for salmonella. Is this sufficient evidence for the USDA to state that the prevalence of salmonella in the region’s water differs from the prevalence of salmonella in the region’s wildlife? Use α = .01 to make your decision
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Statistics for Business and Economics (13th Edition)
- According to the article “Rubbing Hands Together Under Warm Air Dryers Can Counteract Bacteria Reduction” (Infectious Disease News, September 22, 2010) washing your hands isn’t enough—good “hand hygiene” also includes drying hands thoroughly. The article described an experiment to compare bacteria reduction for three different hand-drying methods. In this experiment, subjects handled uncooked chicken for 45 seconds, then washed their hands with a single squirt of soap for 60 seconds, and then used one of the three hand-drying methods. After completely drying their hands, the bacteria count on their hands was measured. Suppose you want to carry out a similar experiment and that you have 30 subjects who are willing to participate. Describe a method for randomly assigning each of the 30 subjects to one of the hand drying methods (Select all that apply) 1)Choose two treatments and sort the subjects by gender. Then assign the men to one treatment and the woment to another treatment.…arrow_forwardOne variety of corn is genetically modified to produce chemicals for defense against predators. The standard corn contains the same standard genotype, but without genetic modification for the chemicals. The two types of corn are then planted in randomly placed adjacent plots across a single field. The amount of predators that are present when the corn has matured are then recorded. The data that was recorded of the predators present among each type are listed. Has genetic alterations decreased the amount of predators for the altered genotype? Normality tests for the populations of both contain a p value less than 0.05. The given alpha is 0.05 Modified Corn (20, 18, 26, 23, 17, 23, 22) Standard Corn (89, 64, 102, 96, 56, 77, 84, 59) use an F test to determine if the variance between the 2 lists are different. Based on this result, state the correct 2 sample parametric test to be used. State the null and alternative. Show calculations while rounding to two decimal points.What is the…arrow_forwardThe Specific Absorption Rate (SAR) for a cell phone measures the amount of radio frequency (RF) energy absorbed by the user’s body when using the handset. Every cell phone emits RF energy. Different phone models have different SAR measures. To receive certification from the Federal Communications Commission (FCC) for sale in the United States, the SAR level for a cell phone must be no more than 1.6 watts per kilogram. A random sample of 20 of the highest SAR level for a random selection of cell phone models as measured by the FCC was collected. Find a 96% confidence interval for the true (population) mean of the Specific Absorption Rates (SARs) for cell phones. Assume that the population standard deviation is σ = 0.337 and the sample mean is 1.024arrow_forward
- FIV (feline immunodeficiency virus) attacks a cat's immune system causing FAIDS (feline acquired immunodeficiency syndrome). It is estimated that between 2 and 25 percent of the global domestic cat population is infected with the virus. FIV is primarily transmitted from cat to cat through biting. A one-step immunochromatographic (IC) test has been developed for the detection of FIV antibodies. It is estimated that 94.7% of cats with FIV test positive and 96.1% of cats without FIV test negative using this test. Assume that 5% of the local cat population is actually infected with FIV.Use this information to answer the following: (a) For a population of 100 000 cats:i. how many are estimated to be infected with FIV?ii. how many of the cats in (a)(i) will test positive? (b) Use your answers from (a) to help construct a 2 x 2 table of counts displaying the results for this sample. Complete the table. (c) Estimate the proportion of local cats that would test negative for FIV but…arrow_forwardFIV (feline immunodeficiency virus) attacks a cat's immune system causing FAIDS (feline acquired immunodeficiency syndrome). It is estimated that between 2 and 25 percent of the global domestic cat population is infected with the virus. FIV is primarily transmitted from cat to cat through biting. A one-step immunochromatographic (IC) test has been developed for the detection of FIV antibodies. It is estimated that 94.7% of cats with FIV test positive and 96.1% of cats without FIV test negative using this test. Assume that 5% of the local cat population is actually infected with FIV. Use this information to answer the following: (a) For a population of 100 000 cats: (i) how many are estimated to be infected with FIV? (ii) how many of the cats in (a)(i) will test positive? (b) Use your answers from (a) to help construct a 2 × 2 table of counts displaying the results for this sample. Complete the table. Estimate the proportion of local cats that would test negative for FIV but actually be…arrow_forwardVermont maple sugar producers sponsored a testing program to determine the benefit of a potential new fertilizer regimen. A random sample of 27 maple trees in Vermont were chosen and treated with one of three levels of fertilizer suggested by the chemical producer. In this experimental setup, nine trees (three in each of three climatic zones) were treated with each fertilizer level and the amount of sap produced (in mL) by the trees in the subsequent season was measured. The results are presented in the following table. Southern Zone Central Zone Northern Zone 76.2 80.4 74.2 79.4 87.9 86.9 84.5 85.2 80.1 Low fertilizer Medium 87.0 95.1 93.0 98.2 94.7 96.2 88.4 90.4 922 fertilizer High 84.2 87.5 83.1 90.3 89.9 93.2 81.4 84.7 82.2 fertilizer Estimate the main effects of fertilizer levels and climatic zone, and their interactions. b. Construct an ANOVA table. You may give ranges for the P-values. Test the hypothesis that there is no interaction between fertilizer levels and climatic zone.…arrow_forward
- Vasectomies and Prostate Cancer. In the United States, approximately 450,000 vasectomies are performed each year. In this surgical procedure for contraception, the tube carrying sperm from the testicles is cut and tied. Several studies have been conducted to analyze the relationship between vasectomies and prostate cancer. The results of one such study by E. Giovannucci et al. appeared in the paper “A Retrospective Cohort Study of Vasectomy and Prostate Cancer in U.S. Men” (Journal of the American Medical Association, Vol. 269(7), pp. 878–882). Of 21,300 men who had not had a vasectomy, 69 were found to have prostate cancer; of 22,000 men who had had a vasectomy, 113 were found to have prostate cancer. a. At the 1% significance level, do the data provide sufficient evidence to conclude that men who have had a vasectomy are at greater risk of having prostate cancer? Consider men who had had a vasectomy Population 2. b. Is this study a designed experiment or an observational study?…arrow_forwardInorganic phosphorous is a naturally occurring element in all plants and animals, with concentrations increasing progressively up the food chain (fruit < vegetables < cereaise nuts < corpse). Geochemical surveys take soil samples to determine phosphorous content (in ppm, parts per million). A high phosphorous content may or may not indicate an ancient burial site, food storage site, or even a garbage dump. Independent random samples from two regions gave the following phosphorous measurements (in ppm). Assume the distribution of phosphorous is mound-shaped and symmetric for these two regions. Region It x n, 15 857 1,551 1,230 875 1,080 2,330 1,850 1,860 2,340 1,080 910 1,130 1,450 1,260 1,010 Region III xi n 14 542 B06 1,230 1,770 790 960 1,650 860 890 640 1,180 1,160 1,050 1,020 A USE SALT (a) Use a caiculator with mean and standard deviation keys to verify that a and s (Round your answers to four decimal places.) ppm ppm ppm ppm (b) Let , be the population mean for x, and let be the…arrow_forwardA deficiency of the trace element selenium in the diet can negatively impact growth, immunity, muscle and neuromuscular function, and fertility. The introduction of selenium supplements to dairy cows is justified when pastures have low selenium levels. Authors of a research paper supplied the following data on milk selenium concentration (mg/L) for a sample of cows given a selenium supplement (the treatment group) and a control sample given no supplement, both initially and after a 9-day period. Initial Measurement Treatment Control 11.4 9.1 9.6 8.7 10.1 9.7 8.5 10.8 10.2 10.9 10.6 10.6 11.9 10.1 9.9 12.3 10.7 8.8 10.2 10.4 10.3 10.9 11.4 10.4 9.3 11.6 10.6 10.9 10.9 8.3 After 9 Days Treatment Control 138.3 9.2 104 8.9 96.4 8.9 89 10.1 88 9.6 103.8 8.6 147.3 10.4 97.1 12.4 172.6 9.2 146.3 9.5 99 8.4 122.3 8.8 103 12.5 117.8 9.1 121.5 93 (a) Use the given data for the treatment group to determine if…arrow_forward
- A deficiency of the trace element selenium in the diet can negatively impact growth, immunity, muscle and neuromuscular function, and fertility. The introduction of selenium supplements to dairy cows is justified when pastures have low selenium levels. Authors of a research paper supplied the following data on milk selenium concentration (mg/L) for a sample of cows given a selenium supplement (the treatment group) and a control sample given no supplement, both initially and after a 9-day period. Initial Measurement Treatment Control 11.3 9.1 9.7 8.7 10.1 9.7 8.5 10.8 10.4 10.9 10.7 10.6 11.8 10.1 9.8 12.3 10.6 8.8 10.4 10.4 10.2 10.9 11.3 10.4 9.2 11.6 10.7 10.9 10.8 8.2 After 9 Days Treatment Control 138.3 9.4 104 8.8 96.4 8.8 89 10.1 88 9.7 103.8 8.7 147.3 10.3 97.1 12.3 172.6 9.4 146.3 9.5 99 8.3 122.3 8.9 103 12.5 117.8 9.1 121.5 93 (a) Use the given data for the treatment group to determine if…arrow_forwardA deficiency of the trace element selenium in the diet can negatively impact growth, immunity, muscle and neuromuscular function, and fertility. The introduction of selenium supplements to dairy cows is justified when pastures have low selenium levels. Authors of a research paper supplied the following data on milk selenium concentration (mg/L) for a sample of cows given a selenium supplement (the treatment group) and a control sample given no supplement, both initially and after a 9-day period. Initial Measurement Treatment Control 11.2 9.1 9.6 8.7 10.1 9.7 8.5 10.8 10.3 10.9 10.6 10.6 11.7 10.1 9.7 12.3 10.8 8.8 10.3 10.4 10.4 10.9 11.2 10.4 9.4 11.6 10.6 10.9 10.7 8.4 After 9 Days Treatment Control 138.3 9.3 104 8.7 96.4 8.7 89 10.1 88 9.6 103.8 8.6 147.3 10.2 97.1 12.2 172.6 9.3 146.3 9.5 99 8.2 122.3 8.9 103 12.5 117.8 9.1 121.5 93 (a) Use the given data for the treatment group to determine if there…arrow_forwardVitamin D is important for maintaining strong bones by helping the body absorb calcium from food and sup-plements. The recommended amount of vitamin D is 400 IU (international units) per day. Many people take vitamin D supplements, often at levels greatly exceeding the recommended daily amount. What is the effect of taking too much vitamin D? Researchers investigated this in a double-blind randomized clinical trial. Subjects were divided into three groups. One, consisting of 109 subjects, took 400 IU per day for three years. second group, consisting of 100 subjects, took 4,000 IU per day for three years. A third group, consisting of 102 subjects, took 10,000 IU per day for three years. The total volumetric bone mass density of the tibia (the large bone located in the lower front portion of the leg, sometimes referred to as the shinbone) was measured in order to assess the effect of the different dosages of Vitamin D.11 The degrees of freedom for the ANOVA F statistic comparing the mean…arrow_forward
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