Food intake of grazing animals is limited by the rate grass can be chewed and swallowed, as well as the rate at which food can be digested. The authors of the paper “What Constrains Daily Intake in Thomson’s Gazelles?” (Ecology [1999]: 2338–2347) observed the grazing activity of captive Thomson’s gazelles. They recorded grazing rate (amount of grass eaten, in grams per minute) and biomass of the grazing area (food density, in grams per square meter).
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Introduction To Statistics And Data Analysis
- The article “Withdrawal Strength of Threaded Nails” (D. Rammer, S. Winistorfer, and D. Bender, Journal of Structural Engineering 2001:442–449) describes an experiment comparing the ultimate withdrawal strengths (in N/mm) for several types of nails. For an annularly threaded nail with shank diameter 3.76 mm driven into spruce-pine-fir lumber, the ultimate withdrawal strength was modeled as lognormal with μ = 3.82 and σ = 0.219. For a helically threaded nail under the same conditions, the strength was modeled as lognormal with μ = 3.47 and σ = 0.272. a) What is the mean withdrawal strength for annularly threaded nails? b) What is the mean withdrawal strength for helically threaded nails? c) For which type of nail is it more probable that the withdrawal strength will be greater than 50 N/mm? d) What is the probability that a helically threaded nail will have a greater withdrawal strength than the median for annularly threaded nails? e) An experiment is performed in which withdrawal…arrow_forwardSecond-Hand Smoke: Data Set 12 “Passive and Active Smoke” in Appendix B includes cotinine levels measured in a group of nonsmokers exposed to tobacco smoke (n = 40, Mean = 60.58 ng>mL, s = 138.08 ng>mL) and a group of nonsmokers not exposed to tobacco smoke (n = 40, Mean = 16.35 ng>mL, s = 62.53 ng>mL). Cotinine is a metabolite of nicotine, meaning that when nicotine is absorbed by the body, cotinine is produced. Use a 0.05 significance level to test the claim that nonsmokers exposed to tobacco smoke have a higher mean cotinine level than nonsmokers not exposed to tobacco smoke. Construct the confidence interval appropriate for the hypothesis test in part a. What do you conclude about the effects of second-hand smoke?arrow_forwardAn article in Technometrics (1974, Vol. 16, pp. 523–531) considered the following stack-loss data from a plant oxidizing ammonia to nitric acid. Twenty-one daily responses of stack loss (the amount of ammonia escaping) were measured with air flow x1, temperature x2, and acid concentration x3. y = 42, 37, 37, 28, 18, 18, 19, 20, 15, 14, 14, 13, 11, 12, 8, 7, 8, 8, 9, 15, 15 x1 = 80, 80, 75, 62, 62, 62, 62, 62, 58, 58, 58, 58, 58, 58, 50, 50, 50, 50, 50, 56, 70 x2 = 27, 27, 25, 24, 22, 23, 24, 24, 23, 18, 18, 17, 18, 19, 18, 18, 19, 19, 20, 20, 20 x3 = 89, 88, 90, 87, 87, 87, 93, 93, 87, 80, 89, 88, 82, 93, 89, 86, 72, 79, 80, 82, 91 (a) Fit a linear regression model relating the results of the stack loss to the three regressor variables. (b) Estimate σ2. (c) Find the standard error se(βj). (d) Use the model in part (a) to predict stack loss when x1 = 60, x2 = 26, and x3 = 85.arrow_forward
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- An article in Biotechnology Progress [“Optimization of Conditions for Bacteriocin Extraction in PEG/Salt Aqueous Two-Phase Systems Using Statistical Experimental Designs” (2001, Vol. 17, pp. 366–368)] reported an experiment to investigate and optimize the extraction of nisin in aqueous two-phase systems (ATPS). Nisin recovery was the dependent variable (y). The two regressor variables were the concentration (%) of PEG 4000 (indicated as x1) and the concentration (%) of Na2SO4 (indicated as x2). The data is shown below. a) Find the fit parameters of the proposed model. b) Establish, by means of a hypothesis test, if the regression is significant. c) State, if the regression coefficients are significant. d) Evaluate R2 as well as R_adjusted^2. e) Construct and analyze the residual plot.arrow_forwardThe amount of pollution produced by cars was measured for cars using gasoline containing different amounts of lead. A. Independent B. Dependentarrow_forwardThe efficiency ratio for a steel specimen immersed in a phosphating tank is the weight of the phosphate coating divided by the metal loss (both in mg/ft2). The article “Statistical Process Control of a Phosphate Coating Line” (Wire J. Intl., May 1997: 78–81) gave the accompanying data on tank temperature (x) and efficiency ratio (y).Temp. 170 172 173 174 174 175 176Ratio .84 1.31 1.42 1.03 1.07 1.08 1.04Temp. 177 180 180 180 180 180 181Ratio 1.80 1.45 1.60 1.61 2.13 2.15 .84Temp. 181 182 182 182 182 184 184Ratio 1.43 .90 1.81 1.94 2.68 1.49 2.52Temp. 185 186 188Ratio 3.00 1.87 3.08a. Construct stem-and-leaf displays of both temperature and efficiency ratio, and comment on interesting features.b. Is the value of efficiency ratio completely and uniquely determined by tank temperature? Explain your reasoning.c. Construct a scatterplot of the data. Does it appear that efficiency ratio could be very well predicted by the value of temperature? Explain your reasoning.arrow_forward
- A survey among the workers in a large manufacturing company was taken, in order to findout from which company the workers had purchased their mobile phones, and to find outwhether the choice of mobile phone company was related to the type of worker. The resultsare shown in the table below. ls there evidence, at 5% level, that the choice of Phone Company is independent of the type ofworker?arrow_forwardA study of Spring Peeper breeding yielded the results in the table below. Spring Peepers were bred in different temperature controlled environments. The concentration of dissolved oxygen was measured in each environment. Temperature of water (⁰C) Dissolved oxygen in freshwater (mg/L) Number of eggs hatched into tadpoles 8 10.0 80 8 12.0 100 8 13.5 120 8 16.0 150 15 8.0 600 15 9.5 1090 15 12.0 1700 15 14.0 2190 22 6.5 870 22 8.5 1450 22 10.5 1970 22 12.0 2450 29 5.5 110 29 7.0 210 29 9.0 400 29 11.0 500 Graph the data in the table linked in the description above. (Hint: You must identify the dependent variable and two independent variables.) You may complete your graph electronically or by hand (then take a photo of your graph). Upload your photo or electronic file. (COMPLETE IN ONE GRAPH).arrow_forwardFor some genetic mutations, it is thought that the frequency of the mutant gene in men increases linearly with age. If m1 is the frequency at age t1, and m2 is the frequency at age t2, then the yearly rate of increase is estimated by r = (m2 − m1)/(t2 − t1). In a polymerase chain reaction assay, the frequency in 20-year-old men was estimated to be 17.7 ± 1.7 per μgDNA, and the frequency in 40-year-old men was estimated to be 35.9 ± 5.8 per μg DNA. Assume that age is measured with negligible uncertainty.a) Estimate the yearly rate of increase, and find the uncertainty in the estimate.b) Find the relative uncertainty in the estimated rate of increase.arrow_forward
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