At a 95% confidence interval for p, the proportion of all US adults who exercise regularly is 0.562 to 0.684. Is it reasonable to believe more than two-thirds of US adults exercise regularly?
A computer company wants to determine if there is a difference in the proportion of defective computer chips in a day’s production from two different production plants, A and B. A quality control specialist takes a sample of 100 chips from the first hour of production from plant A and determines that there are 12 defective chips. The specialist then takes a sample of 100 chips from the last hour of production from plant B and determines that there are 10 defective chips. He wants to construct a 90% confidence interval for the true difference in proportions of defective chips from a day’s production between the two plants. Are the conditions for inference met?
A statistics class weighed 20 bags of grapes purchased from the store. The bags are advertised to contain 16 ounces, on average. The class calculated the 90% confidence interval for the true mean weight of bags of grapes from this store to be (15.875, 16.595) ounces. Is the store justified in stating that the average weight of the bags of grapes is 16 ounces?
A recent report stated that over half of food delivery drivers eat some of the food they are delivering. A 95% confidence interval for the true proportion of food delivery drivers who eat some of the food they are delivering is (0.398, 0.706). Is it reasonable to believe more than half of food delivery drivers eat some of the food they are delivering?
A guidance counselor is studying test anxiety in freshman students. A random sample of 972 high school freshmen finds that 219 of these students have had some form of test anxiety. A 95% confidence interval for the proportion of freshmen with test anxiety is (0.199, 0.252). Which statement correctly interprets the interval?
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