Practise using the 68–95–99.7 rule to estimate normal-distribution percentages, combine symmetric regions, and locate intervals one to three standard deviations from the mean.
The distribution of the sale price of a certain car model is approximately normal with a mean of 65,500 and a standard deviation of $3,100. Based on the distribution, which of the following is an appropriate conclusion?
Approximately 95\% of the cars of this model have a sale price of less than $66,700.
Approximately 99\% of the cars of this model have a sale price between $57,500 and $73,500.
The interquartile range of the car model's sale price is approximately $6,200.
The maximum of the car model's sale price is $69,800.
Approximately 84\% of the cars of this model have a sale price greater than $57,400. A scam call is a call made to deceive the person receiving the call. A report claims that 45 percent of all calls received on mobile phones can be classified as scam calls. A mobile phone service believes that the percent of scam calls is different than the 45 percent claimed in the report. Let P represent the population of mobile phone calls that can be classified as scam calls. A random sample of calls received on mobile phone devices was selected in order to construct a 95 percent confidence interval for estimating P.
B