Question

3. The U.S. Geological Survey compiled historical data about Old Faithful Geyser (Yellowstone National Park) from 1870 to 1987. Let x1 be a random variable that represents the time interval (in minutes) between Old Faithful eruptions for the years 1948 to 1952. Based on 9,800 observations, the sample mean interval was 62.6 minutes. Let x2 be a random variable that represents the time interval in minutes between Old Faithful eruptions for the years 1983 to 1987. Based on 24,404 observations, the sample mean time interval was 69.4 minutes. Historical data suggest that σ1 = 9.40 minutes and σ2 = 12.55 minutes. Let μ1 be the population mean of x1and let μ2 be the population mean of x2.

Construct a 95% confidence interval for µ1 - µ2. & state your conclusion in terms of the problem.

Answer 1