If the variance of X is 45 then the variance of 2X is A 225

If the variance of X is 4.5, then the variance of 2X is:
A. 2.25.
B. 9.
C. 18.
D. 4.5

Which of the following variables is always discrete?.
A. The amount of frustration resulting from a minor car accident.
B. The amount of time a car is in the shop after a minor accident.
C. The depth of a dent caused by a minor accident.
D. The cost to repair a car after a minor accident.

2. The San Francisco Bay Area\'s commuter rail system is called BART, short for Bay Area Rapid Transit. The BART system consists of 95 miles of track and 39 stations. In the 2001 fiscal year, passengers took over 97 million trips by BART.

The average BART trip length in fiscal year 2001 was 13.00 miles. Assume the standard deviation for a trip is 8.2 miles. If we took a SRS of 46 BART trips, what is the distribution of x, the sample mean trip length?
A. The shape of the distribution is unknown, but it has mean 13.00 and standard deviation 8.2 miles.
B. The shape of the distribution is unknown, but it has mean 13.00 and standard deviation 1.21 miles.
C. Approximately Normal with mean 13.00 and standad deviation 8.21 miles.
D. Approximately Normal with mean 13.00 and standard deviation 1.21 miles.

According to BART\'s 2001 annual report, 92.2% of all trains were on time in that year. If we assume that the probability a train was on time in 2001 was .922, which of the following is true?
A. The probability that a train was early was -.078.
B. The probability that two trains in a row were on time was 1.844.
C. The probability that a train was early was .078.
D. None of the above.

Solution