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Question 8 (3 points) A cellular telephone company recently conducted research into the length of calls (in minutes) made by customers. In a random sample of 30 calls, the sample mean was x= 18.6 minutes and the standard deviation was s = 5.2 minutes. Construct and interpret a 90% confidence interval for true mean call length. (4-step process) BIU S' S. Record Answer Question 9 (3 points) In an extensive government study conducted this year, a simple random sample of 500 households was obtained and 80 had experienced property damage due to a crime. (a) Calculate and interpret a 95% confidence interval for the true proportion of households that have experienced property damage due to crime. (4-step process) (b) Last year, it was found that the proportion of households that had been damaged due to crime was 0.20. Based on your interval from part (a), is there convincing evidence that the proportion of households damaged due to crime has decreased from 0.20? Explain