A randomly selected sample of n = 51 men in Brazil had an average lifespan of 59 years. The standard deviation was 10 years, and the standard error of the mean is 1.400. Calculate a 90% confidence interval for the average lifespan for all men in Brazil.
A) (42.2, 75.8)
B) (56.6, 61.4)
C) (56.2, 61.8)
D) None of the above

Question

Quizplus · Accepted Answer

The 90% confidence interval is calculated using the formula: mean ± (z-score * standard error of the mean). For a 90% confidence level, the z-score is approximately 1.645. Given the mean of 59 years and the standard error of 1.400, the calculation is 59 ± (1.645 * 1.400), which equals 59 ± 2.3, resulting in a confidence interval of (56.7, 61.3). Choice B (56.6, 61.4) is the closest to this calculation.

A Randomly Selected Sample of N = 51 Men in Brazil