# A survey shows that 30 of university students smoke

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Chapter 12 / Exercise 23
Nature of Mathematics
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17.A survey shows that 30% of university students smoke.If 7 university students areselected at random, find each of the following:a.the probability that exactly 2 of them smoke.b.the probability that at most 2 of them smoke.18.The waiting times at a hospital are normally distributed with a mean of 11 minutes anda standard deviation of 4 minutes.a.Find the probability that a patient has to wait less than 17.6 minutes at this hos-pital.b.Find the waiting timeTfor which 78% of the patients wait more thanTminutesat such a hospital.9
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Chapter 12 / Exercise 23
Nature of Mathematics
Smith Expert Verified
19.Based on a simple random sample, a 99% confidence intercal for a population proportionis given by(0.43,0.47)a.Find the sample proportion ˆp, and the margin of errorE.b.Find the necessary sample sizento obtain the above confidence interval.20.A statistics professor wants to make a 95% confidence interval for the proportion of allstudents who have iPhones and wants the margin of error to beE= 0.05.a.If no prior estimate of the sample proportion is known, what sample size is necessaryto construct such a confidence interval?b.If the sample proportion is estimated by 0.35, how large should the sample size be?10
21.From a simple random sample of 716 Americans, it was found that 164 are without healthinsurance coverage. Construct a 98% confidence interval to estimate the proportion ofall Americans who lack health insurance.22.Find the following:a.thet-score for whichdf= 25 and the area to the right of it is 0.005.b.thet-score for whichdf= 33 and the area to the left of it is 0.95.c.t0.01for whichdf= 37.11
23.Based on a simple random sample of 38 adult males in North America, it is found thatthe average height is 170cm with a sample standard deviation of 8cm.Construct a99% confidence interval for the mean height of all adult males in North America.12
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