The speed at which you can log into a website through a smart phone is an important quality characteristic of that website. In a recent test, the mean time to log into the JetBlue Airways website through a smart phone was 4.237 seconds. (Data extracted from N. Trejos, "Travelers Have No Patience for Slow Mobile Sites," USA Today, April 4, 2012, p. 3B.) Suppose that the download time is normally distributed, with a standard deviation of 1.3 seconds. What is the probability that a download time is
a. Less than 2 seconds?
b. Between 1.5 and 2.5 seconds?
c. Above 1.8 seconds?
d. 99% of the download times are slower (higher) than how many seconds?
e. 95% of the download times are between what two values, symmetrically distributed around the mean?
f. Suppose that the download times are uniformly distributed between 1 and 9 seconds. What are your answers to (a) through (c)?