A blood lead level of 70 mg/ml has been commonly accepted as safe. However, researchers have noted that some neurophysiological symptoms of lead poisoning appear in people whose blood lead levels are below 70 mg/ml. The article “Subclinical Neuropathy at Safe Levels of Lead Exposure” (Archives of Environmental Health [1975]: 180–183) gave the following nerve-conduction velocities for a group of workers who were exposed to lead in the workplace but whose blood lead levels were below 70 mg/ml and for a group of controls who had no exposure to lead:
Use a level 0.05 rank-sum test to determine whether there is a significant difference in mean conduction velocity between workers exposed to lead and those not exposed to lead.
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Introduction to Statistics and Data Analysis
- 1. Captopril is a drug designed to lower systolic blood pressure. When subjects were treated with this drug, their systolic blood pressure readings (in mm Hg) were measured before and after the drug was taken. Results are given in the accompanying tables (based on data from "Essential Hypertension: Effect of an Oral Inhibitor of Angiotensin-Converting Enzyme," by MacGregor et al., British Medical Journal, Vol. 2). Using a 0.01 significance level, is there sufficient evidence to support the claim that captopril is effective in lowering systolic blood pressure? Subject Before (x) 200 After (y) А В C D E F G H I K 174 198 170 179 182 193 209 185 155 169 210 191 170 177 167 159 151 176 183 159 145 146 177 2. A study was conducted to investigate the effectiveness for randomly selected subjects are given in the accompanying table (based on "An Analysis of hypnotism in reducing pain. Results Factors That Contribute to the Efficacy of Hypnotic Analgesia," by Price and Barber, Journal of…arrow_forwardA study was conducted to examine the effect of diet cola consumption on calcium levels in women. A sample of 16 healthy women aged 18 to 40 were randomly assigned to drink 24 ounces of either diet cola or water. Their urine was collected for three hours after ingestion of the beverage and calcium excretion (in mg) was measured. The data are stored in ColaCalcium.arrow_forwardFoot ulcers are a common problem for people with diabetes. Higher skin temperatures on the foot indicate an increased risk of ulcers. The article "An Intelligent Insole for Diabetic Patients with the Loss of Protective Sensation" (Kimberly Anderson, M.S. Thesis, Colorado School of Mines), reports measurements of temperatures, in °F, of both feet for 181 diabetic patients. The results are presented in the following table. Left Foot Right Foot 80 80 85 85 75 80 88 86 89 87 87 82 78 78 88 89 89 90 76 81 89 86 87 82 78 78 80 81 87 82 86 85 76 80 88 89 Construct a scatterplot of the right foot temperature (y) versus the left foot temperature (x). Verify that a linear model is appropriate. b. Compute the least-squares line for predicting the right foot temperature from the left foot temperature. If the left foot temperatures of two patients differ by 2 degrees, by how much would you predict their right foot temperatures to differ? Predict the right foot temperature for a patient whose left…arrow_forward
- Estriol Level and Birth Weight. J. Greene and J. Touchstone conducted a study on the relationship between the estriol levels of pregnant women and the birth weights of their children. Their findings, “Urinary Tract Estriol: An Index of Placental Function,” were published in the American Journal of Obstetrics and Gynecology (Vol. 85(1), pp. 1–9). The data from the study are provided on the WeissStats site, where estriol levels are in mg/24 hr and birth weights are in hectograms. a. Decide whether finding a regression line for the data is reasonable. If so, then also do parts (b)–(d). b. Obtain the coefficient of determination. c. Determine the percentage of variation in the observed values of the response variable explained by the regression, and interpret your answer. d. State how useful the regression equation appears to be for making predictions.arrow_forwardPLS SHOW COMPLETE SOLUTION. DONT ROUND OFF. USE Z-TABLE.arrow_forward2. A case-control (or retrospective) study was conducted to investigate a relationship between the colors of helmets worn by motorcycle drivers and whether they are injured or killed in a crash. Results are given in the table below (based on data from “Motorcycle Rider Conspicuity and Crash Related Injury: Case-Control Study”, by Wells et al., BMJ USA, Vol. 4). 1. Test the claim that injuries are independent of helmet color, using chisq.test function in R at a 0.05 significance level. Please state the hypothesis, present a screenshot of the R output for this test, and provide your conclusion in the context of the problem. 2. Should motorcycle drivers choose helmets with a particular color? If so, which color appears best? Provide your justification.arrow_forward
- please show diagram of p valuearrow_forwardHIV/AIDS patients are regularly monitored for their CD4 counts in order to make sure that antiretroviral therapies are effectiveSuppose the distribution of CD4 counts in a population is approximately normal with mu = 237 and sigma = 43 . HIV patients are defined as moving into the AIDS stage of their disease course after their CD4 counts are less than 200. What proportion of patients in this population is suffering from AIDS?arrow_forwardTwo researchers conduct separate studies to test Ho: p=0.50 against Ha: p0.50, each with n = 400. Researcher A gets 226 observations in the category of interest, and p= 6=226/400=0.565. Researcher B gets 225 in the category of interest, and p = 225/400=0.5625. Complete parts (a) through (d) below. a. Find the z-scores and P-values for both researchers. Researcher A Z = Researcher B Z = P-value = P-value = (Round the z-scores to two decimal places as needed. Round the P-values to three decimal places as needed.) The result in case A is The result in case B is b. Using α = 0.01, indicate in each case whether the result is "statistically significant." Interpret. What does the statistical significance of the results above imply? OA. A difference in conclusions between two hypothesis tests does not necessarily mean that the test with the result that is deemed "statistically significant" is actually much more significant than the test with the result that is deemed "not statistically…arrow_forward
- Are seatbelts effective at saving lives? We wish to examine whether or not the use of seatbelts reduces fatalities at the a = 0.01 level of significance. Let pN represent the proportion of non-seatbelt wearing passengers who were involved in a crash and died and py represent the proportion of seatbelt wearing passengers who were involved in a crash and died. NOTE: The data used in this study were obtained through observational study...no experiment was conducted! Which would be correct hypotheses for this test? O Ho:PN = pY, H1:PN > pY Ho: PN = pY, H,:PN Py In a random sample of 321 non-seatbelt wearing passengers involved in a car crash, 30 were killed. In a random sample of 492 seatbelt wearing passengers involved in a car crash, 13 were killed. Find the test statistic (2 decimal places): Give the P-value (4 decimal places - if less than 0.001 answer 0): Which is the correct result: Reject the Null Hypothesis O Do not Reject the Null Hypothesis Which would be the appropriate…arrow_forwardAn article in Knee Surgery, Sports Traumatology, Arthroscopy (2005, Vol. 13, pp. 273-279), considered arthroscopic meniscal repair with an absorbable screw. Results showed that for tears greater than 25 millimeters, 15 of 17 repairs were successful while for shorter tears, 22 of 31 repairs were successful. (a) Is there evidence that the success rate is greater for longer tears? Use a = 0.05.What is the P-value? (b) Calculate a one-sided 95% confidence bound on the difference in proportions that can be used to answer the question in part (a). (a) There evidence that the success rate is greater for longer tears. The P-value is Round your answer to four decimal places (e.g. 98.7654). (b) The one-sided 95% confidence bound is SPi - P2. Round your answer to three decimal places (e.g. 98.765).arrow_forward10.2.14 An article in Quality Engineering [2012, Vol. 24(1)] described an experiment on a grinding wheel. The following are some of the grinding force data (in N) from this experiment at two different vibration levels. Low 242, 249, 235, 250, 254, 244, 258, 311, 237, 261, 314, 252 High 302, 421, 419, 399, 317, 311, 350, 363, 392, 367, 301, 302 a. Is there evidence to support the claim that the mean grind- ing force increases with the vibration level? b. Find a 95% confidence interval for the difference in the mean grinding force for the two vibration levels. c. Is the value zero contained in the 95% confidence interval? Explain the connection with the conclusion you reached in part (a). d. Do normal probability plots of grinding force indicate any violations of the assumptions for the tests and confidence interval that you performed?arrow_forward
- Glencoe Algebra 1, Student Edition, 9780079039897...AlgebraISBN:9780079039897Author:CarterPublisher:McGraw Hill