Concept explainers
The article “Flexure of Concrete Beams Reinforced with Advanced Composite Orthogrids” (J. of Aerospace Engr., 1997: 7–15) gave the accompanying data on ultimate load (kN) for two different types of beams. Sample Sample Sample Type Size Mean SD Fiberglass grid 26 33.4 2.2 Commercial 26 42.8 4.3 carbon grid
Type | Sample Mean | Sample SD | |
Fiberglass grid | 26 | 33.4 | 2.2 |
Commercial | 26 | 42.8 | 4.3 |
carbon grid |
a. Assuming that the underlying distributions are normal, calculate and interpret a 99% CI for the difference between true average load for the fiberglass beams and that for the carbon beams.
b. Does the upper limit of the interval you calculated in part (a) give a 99% upper confidence bound for the difference between the two μ’s? If not, calculate such a bound. Does it strongly suggest that true average load for the carbon beams is more than that for the fiberglass beams? Explain.
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Chapter 9 Solutions
Probability and Statistics for Engineering and the Sciences
- Snow avalanches can be a real problem for travelers in the western United States and Canada. A very common type of avalanche is called the slab avalanche. These have been studied extensively by David McClung, a professor of civil engineering at the University of British Columbia. Suppose slab avalanches studied in a region of Canada had an average thickness of u = 67 cm. The ski patrol at Vail, Colorado, is studying slab avalanches in its region. A random sample of avalanches in spring gave the following thicknesses (in cm). 59 51 76 38 65 54 49 62 68 55 64 67 63 74 65 79 (i) Use a calculator with sample mean and standard deviation keys to find x and s. (Round your answers to two decimal places.) X= cm S= cm (ii) Assume the slab thickness has an approximately normal distribution. Use a 1% level of significance to test the claim that the mean slab thickness in the Vail region is different from that in the region of Canada. (a) What is the level of significance? State the null and…arrow_forwardAn experiment was conducted to determine the effect of machining factors on ceramicstrength. Two levels of table speed (slow and fast), two directions (longitudinal and transverse) and two levelsof wheel grit (I and II) were identified by the researcher. The experiment was replicated three times and thestrength of each randomly selected ceramic was obtained. The ANOVA table of the results of the analysis areas follows. 1. Refer to the ANOVA table at a=0.01, what is the conclusion for testing significance in 3-way interaction Reject/Fail to Reject Ho 2. If sequential test of hypothesis is performed the following are (True or False)? a. All 2-way interaction effects are going to be tested b. All main effects are going to be tested 3. What combination of effects will result to a significant result at a=0.01 if should all test are going to be performed among the main effects and two way interactions? (choose 1pair/combination: direction, wheel grit, speed)arrow_forwardThe yield of alfalfa from a random sample of six test plots is 1.4, 1.6, 0.9, 1.9, 2.2,and 1.2 tons per acre. Assume the data can be looked upon as a sample from anormal population. Test at the 0.05 level of significance whether this supports thecontention that the average yield for this kind of alfalfa is 1.5 tones per acre.arrow_forward
- (1) Two rubber compounds were tested for tensile strength and the fol- lowing values were found A : 32,30,33, 32, 29, 34, 32 B: 33,35, 36, 37,35, 34 Under the assumption that the two populations are normally distributed, test the hypothesis that the average tensile strength of the two rubber compounds is different using significance level a = 0.01 and a = 0.05.arrow_forwardThe article “Arsenic and Mercury in Lake Whitefish and Burbot Near the Abandoned Giant Mine on Great Slave Lake” (P. Cott, B. Zajdlik, et al., Journal of Great Lakes Research, 2016:223–232) presents measurements of arsenic concentrations in fish found in Northern Canada. a) In a sample of 8 whitefish caught in Yellowknife Bay, the mean arsenic concentration in the liver was 0.32 mg/kg, with a standard deviation of 0.05 mg/kg. Find a 95% confidence interval for the concentration in whitefish found in Yellowknife Bay. b) In a sample of 8 whitefish caught in Baker Pond, the mean arsenic concentration in the liver was 0.55 mg/kg, with a standard deviation of 0.36 mg/kg. Should the Student’s t distribution be used to find a 95% confidence interval for the concentration in whitefish found in Baker Pond? If so, find the confidence interval. If not, explain why not.arrow_forwardA recent Nielsen analysis found that the typical U.S. smartphone user is spending an average of 220 minutes per day using apps. We speculate that the average time spent using apps for Generation X smartphone users (aged 41-56 years) is less than the national average. The hypotheses are Ho: H = 220 minutes versus Ha: µ < 220 minutes. Summary results from R are provided. Summary Statistics Std. Dev (s) Mean Sample Size (n) 205 minutes 63.25 minutes 31arrow_forward
- The amount of flow through a solenoid valve in an automobile’spollution-control system is an important characteristic.An experiment was carried out to study howflow rate depended on three factors: armature length,spring load, and bobbin depth. Two different levels (lowand high) of each factor were chosen, and a singleobservation on flow was made for each combination oflevels. The resulting data set consisted of how manyobservations?arrow_forwardDetermine the kurtosis if the data given is a sample.arrow_forwardThe article “Arsenic and Mercury in Lake Whitefish and Burbot Near the Abandoned Giant Mine on Great Slave Lake” (P. Cott, B. Zajdlik, et al., Journal of Great Lakes Research, 2016:223–232) presents measurements of arsenic concentrations in fish found in Northern Canada. In a sample of 8 whitefish caught in Yellowknife Bay, the mean arsenic concentration in the liver was 0.32 mg/kg, with a standard deviation of 0.05 mg/kg. Can you conclude that the mean arsenic concentration in whitefish in Yellowknife Bay is greater than 0.3 mg/kg?arrow_forward
- The amount of chlorine in 100 cm3 water taken from a water tank was measured, the average was 2.15 mg was found. The expert claims that the amount of chlorine in the water is greater than that measured. For this reason, 100 households were randomly selected, with an average chlorine content of 2.55mg and a variance of 0.49 mg. According to this data, find the account value z. 13 - O A) 8,15 O B) 5,71 O C) -5,71 O D) -8, 15 O E) 0.54arrow_forwardBlood cocaine concentration (mg/L) was determinedboth for a sample of individuals who had died fromcocaine-induced excited delirium (ED) and for a sampleof those who had died from a cocaine overdose withoutexcited delirium; survival time for people in bothgroups was at most 6 hours. The accompanying datawas read from a comparative boxplot in the article“Fatal Excited Delirium Following Cocaine Use” (J.of Forensic Sciences, 1997: 25–31). ED 0 0 0 0 .1 .1 .1 .1 .2 .2 .3 .3.3 .4 .5 .7 .8 1.0 1.5 2.7 2.83.5 4.0 8.9 9.2 11.7 21.0Non-ED 0 0 0 0 0 .1 .1 .1 .1 .2 .2 .2.3 .3 .3 .4 .5 .5 .6 .8 .9 1.01.2 1.4 1.5 1.7 2.0 3.2 3.5 4.14.3 4.8 5.0 5.6 5.9 6.0 6.4 7.98.3 8.7 9.1 9.6 9.9 11.0 11.512.2 12.7 14.0 16.6 17.8 a. Determine the medians, fourths, and fourth spreadsfor the two samples.b. Are there any outliers in either sample? Any extremeoutliers?c. Construct a comparative boxplot, and use it as abasis for comparing and contrasting the ED andnon-ED samples.arrow_forwardThe amount of flow through a solenoid valve in an automobile’spollution-control system is an important characteristic.An experiment was carried out to study howflow rate depended on three factors: armature length,spring load, and bobbin depth. Two different levels (lowand high) of each factor were chosen, and a singleobservation on flow was made for each combination oflevels.a. The resulting data set consisted of how manyobservations?b. Is this an enumerative or analytic study? Explainyour reasoning.arrow_forward
- Glencoe Algebra 1, Student Edition, 9780079039897...AlgebraISBN:9780079039897Author:CarterPublisher:McGraw Hill