Question

PLEASE I HAVE TO FINISH THIS UNTIL TMR

-On each trial of an experiment, a subject is presented with a constant soft noise, which is interrupted at some unpredictable time by a noticeably louder sound. The time it takes for the subject to react to this louder sound is recorded. The following list contains the reaction times (in milliseconds) for the 18 trials of this experiment:
271, 257, 229, 269, 296, 164, 152, 235, 311, 202, 175, 212, 171, 226, 186, 193, 222, 231
Find 40th and 75th percentiles for these reaction times.

Answer 1

• 212, 257

Explanation:

Given

Data set for 18 trials, time in ms

• 271, 257, 229, 269, 296, 164, 152, 235, 311, 202, 175, 212, 171, 226, 186, 193, 222, 231

To find

• 40th and 75th percentiles of the data

Solution

Put the numbers in ascending order

• 152, 164, 171, 175, 186, 193, 202, 212, 222, 226, 229, 231, 235, 257, 269, 271, 296, 311

Get the index

For 40% it is

• 40*18/100 = 7.2
• Rounded up to the nearest whole number, it is 8
• Count the numbers from the left, the 8th number is 212 ms

For 75% it is

• 75*18/100 = 13.5
• Rounded up, to get 14
• Count the 14th number from the left, which is 257 ms