I'm not sure whether to solve with a T test or a Z test because n < 30 (T test), but the standard deviation is known (Z test). How can I figure out which test statistic to use when both test statistics have a condition (ie n < 30 and std dev is known) that is true? Thank you.
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I'm not sure whether to solve with a T test or a Z test because n < 30 (T test), but the standard deviation is known (Z test). How can I figure out which test statistic to use when both test statistics have a condition (ie n < 30 and std dev is known) that is true? Thank you.
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- Suppose that samples of polythene bags from two manufacturers A and B are tested by a prospective buyer for bursting pressure, with the following results: If the prices are the same, which manufacture’s bags would be preferred by the buyer? Why?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…The aging Neotropical termites (Neocapritermes taracua) secrete a sticky, blue-colored liquid that they spew to intruding termites. The younger Neotropical termites secrete a liquid that lacks the blue component, so it is white in appearance. In an experiment that measured the toxicity of the blue substance, the researchers placed one drop of either the blue liquid or the white liquid on individuals of a second termite species, Labiotermes labralis. Of the 41 Labiotermes labralis that got the blue drop, 37 were immobilized. Of the 40 Labiotermes labralis that got the white drop, 9 were immobilized. Is the blue liquid toxic compared to the white liquid?
- In experiments to determine the effectiveness of drugs such as anti-fungal ointments that are applied to the skin, the concentration of the drug in a patient’s skin must be measured. The article “Determining Bioequivalence of Topical Dermatological Drug Products by Tape- Stripping” (W. Navidi, A. Hutchinson, et al., Journal of Pharmacokinetics and Pharmacodynamics, 2008:213–220) describes an improved method of measuring that is designed to ensure that all the drug in the skin is recovered. Assume that in an experiment using the old method, the mean amount of drug recovered from a sample of 49 patients was 105 ng with a standard deviation of 20 ng, and that in an experiment using the new method the mean amount of drug recovered in a sample of 35 patients was 117 ng with a standard deviation of 15 ng. Find a 98% confidence interval for the difference in the mean amounts recovered between the two methods.Researchers interested in lead exposure due to car exhaust sampled the blood of 52 police officers subjected to constant inhalation of automobile exhaust fumes while working traffic enforcement in a primarily urban environment. The blood samples of these officers had an average lead concentration of 124.32 µg/l and an SD of 37.74 µg/l; a previous study of individuals from a nearby suburb, with no history of exposure, found an average blood level concentration of 35 µg/l. Write down the hypotheses that would be appropriate for testing if the police officers appear to have been exposed to a higher concentration of lead. Explicitly state and check all conditions necessary for inference on these data. Test the hypothesis that the downtown police officers have a higher lead exposure than the group in the previous study. Interpret your results in context. Based on your preceding result, without performing a calculation, would a 99% confidence interval for the average blood concentration…The article “Effect of Varying Solids Concentration and Organic Loading on the Performance of Temperature Phased Anaerobic Digestion Process” (S. Vandenburgh and T. Ellis, Water Environment Research, 2002:142–148) discusses experiments to determine the effect of the solids concentration on the performance of treatment methods for wastewater sludge. In the first experiment, the concentration of solids (in g/L) was 43.94 ± 1.18. In the second experiment, which was independent of the first, the concentration was 48.66 ± 1.76. Estimate the difference in the concentration between the two experiments, and find the uncertainty in the estimate.
- A survey of 90 recently delivered women on the rolls of a county welfare department revealed that 27 had a history of intrapartum or postpartum infection. What is the critical value of z if we need to conclude that the population proportion with a history of intrapartum or postpartum infection is less than 0.25.John investigated the quantitative determination of Cr in high-alloy steels by a potentiometric titration of Cr6+. Before titrating, the steel was dissolved in acid and the chromium oxidized to Cr6+ by peroxydisulfate. Following are the results (%w/w Cr) for the analysis of a single reference steel: 16.968, 16.922, 16.840, 16.883, 16.887, 16.977, 16.857, 16.728 Calculate the mean, standard deviation and the 95% confidence interval of the meanResearchers interested in lead exposure due to car exhaust sampled the blood of 52 police officers subjected to constant inhalation of automobile exhaust fumes while working traffic enforcement in a primarily urban environment. The blood samples of these officers had an average lead concentration of 124.32 µg/l and a SD of 37.74 µg/l; a previous study of individuals from a nearby suburb, with no history of exposure, found an average blood level concentration of 35 µg/l. Test the hypothesis that the downtown police officers have a higher lead exposure than the group in the previous study. Interpret your results in context. Based on your preceding result, without performing a calculation, would a 99% confidence interval for the average blood concentration level of police officers contain 35 µg/l? Based on your preceding result, without performing a calculation, would a 99% confidence interval for this difference contain 0? Explain why or why not.
- Researchers interested in lead exposure due to car exhaust sampled the blood of 52 police officers subjected to constant inhalation of automobile exhaust fumes while working traffic enforcement in a primarily urban environment. The blood samples of these officers had an average lead concentration of 124.32 µg/l and a SD of 37.74 µg/l; a previous study of individuals from a nearby suburb, with no history of exposure, found an average blood level concentration of 35 µg/l. Based on your preceding result, without performing a calculation, would a 99% confidence interval for the average blood concentration level of police officers contain 35 µg/l? Based on your preceding result, without performing a calculation, would a 99% confidence interval for this difference contain 0? Explain why or why not.A study was conducted to examine if children with autism spectrum disorder (ASD) had higher prenatal exposure to air pollution, specifically particulate matter < 2.5 g in diameter (PM2.5). Researchers obtained birth records of all children born in Los Angeles between 2000 and 2008 and linked these to the Department of Developmental Services records to determine if any of those subjects had been diagnosed with ASD or not. They used the birth addresses given in the birth records to determine the average daily PM2.5 for the third trimester for each child. The standard deviation for PM2.5 among ASD subjects was found to be 34.6 and for non-ASD subjects was 16.8. Assume PM2.5 is normally distributed. 4a. What was the study design? * Randomized Clinical Trial (RCT) * Case Report * Nested Case-Control Study * Case-Control Study * cross-sectional study Cohort Study 4B. What are the null and alternative hypotheses? 4c. What type of statistical test would you use to analyze the…The sulfate ion concentration in natural water can be determined by measuring the turbidity that results when an excess of BaCl2 is added to a measured quantity of the sample. A turbiditimeter, the instrument used for this analysis, was calibrated with a series of standard Na2SO4 solutions. The following data were obtained for the calibration: