You are interested in purchasing a new car. One of the many points you wish to consider is the resale value of the car after 5 years. Since you are particularly interested in a certain foreign sedan, you decide to estimate the resale value of this car with a 98% confidence interval. You manage to obtain data on 17 recently resold 5-year-old foreign sedans of the same model. These 17 cars were resold at an average price of $12,530 with a standard deviation of $700. Suppose that the interval is calculated to be ($12091.47, $12968.53)
How could we alter the sample size and the confidence coefficient in order to guarantee a decrease in the width of the interval?