126 CHAPTERS 1&2 CUMULATIVE REVIEW CHAPTER 2 Descriptive Statistics In Exercises 1 and 2, identify the sampling technique used, and discuss potential sources of bias (if any). Explain. 1. For quality assurance, every fortieth toothbrush is taken from each of four assembly lines and tested to make sure the bristles stay in the toothbrush. 2. Using random digit dialing, researchers asked 1090 U.S. adults their level of education. 3. In 2020, a worldwide study of workplace fraud found that initial detections of fraud resulted from a tip (43%), an internal audit (15%), management review (12%), by accident (5%), account reconciliation (4%), external audit (4%), document examination (3%), surveillance/monitoring (3%), notified by law enforcement (2%), IT controls (2%), confession (1%), or some other means (6%). Use a Pareto chart to organize the data. (Source: Association of Certified Fraud Examiners) In Exercises 4 and 5, determine whether the number is a parameter or a statistic. Explain your reasoning. 4. In 2021, the median annual salary of a first-year chemist was $58,700. 5. In a survey of 1002 U.S. adults, 64% said that fake news has caused a great deal of confusion or some confusion. (Source: Pew Research Center) 6. The mean annual salary for a sample of electrical engineers is $86,500, with a standard deviation of $1500. The data set has a bell-shaped distribution. (a) Use the Empirical Rule to estimate the percent of electrical engineers whose annual salaries are between $83,500 and $89,500. (b) The salaries of three randomly selected electrical engineers are $93,500, $85,600, and $82,750. Find the z-score that corresponds to each salary. Determine whether any of these salaries are unusual. In Exercises 7 and 8, identify the population and the sample. 7. A survey of 3941 college students in bachelor’s degree programs found that 49% think that the COVID-19 pandemic is likely to negatively impact their ability to complete their degree. (Source: Gallup) 8. A survey of 182 undergraduate and graduate students found that 60% have had difficulty coping with stress in a healthy way. (Source: The JED Foundation) In Exercises 9 and 10, determine whether the study is an observational study or an experiment. Explain. 9. To study the effect of using digital devices in the classroom on exam performance, researchers divided 726 undergraduate students into three groups, including a group that was allowed to use digital devices, a group that had restricted access to tablets, and a control group that was “technologyfree.” (Source: Massachusetts Institute of Technology) 10. In a study of 7847 children in grades 1 through 5, 15.5% have attention deficit hyperactivity disorder. (Source: Journal of Attention Disorders)
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