Question

1. A meteorologist who sampled 13 randomly selected thunderstorms found that the average speed at which they traveled across a certain state was 1.7 miles per hour. The standard deviation of the sample was 1.7 mph. Find the 99% confidence interval of the mean. Do not round the t value from the table. Round the t-interval to one decimal place, example 1.2 < μ < 3.4

   T value from the table for the formula:

   T-interval:  < μ <

Answer 1

The provided sample mean is = 1.7 and the sample standard deviation is s = 1.7. The size of the sample is n = 13 and the required confidence level is 99%.

The degrees of freedom is df=13−1=12, and the significance level is α=0.01.

T value from the table is tc ​= 3.055.

The 99% confidence for the population mean μ is computed using the following expression

CI = (1.7−1.44,1.7+1.44) = (0.26,3.14) (0.3, 3.1)

T-interval: 0.3 < < 3.1