The paper “Modeling and Measurements of Bus Service Reliability” (Transportation Research [1978]:

253– 256) studied various aspects of bus service and presented data on travel times (in minutes) from several different routes. The accompanying frequency distribution is for bus travel times from origin to destination on one particular route in Chicago during peak morning traf fic periods:
Travel Time Frequency Relative Frequency 15 to 16 4 .02 16 to 17 0 .00 17 to 18 26 .13 18 to 19 99 .49 19 to 20 36 .18 20 to 21 8 .04 21 to 22 12 .06 22 to 23 0 .00 23 to 24 0 .00 24 to 25 0 .00 25 to 26 16 .08

a. Construct the corresponding histogram.

b. Compute (approximately) the following percentiles:
i. 86th iv. 95th ii. 15th v. 10th iii. 90th