Aresearcher wondered whether drivers treat bicycle riders differently when they wear helmets. he rigged his bicycle with an ultrasonic sensor that could measure how close each car was that passed him. he then rode on alternating days with and without a helmet. of the 30003000 times that a car passed him, he found that when he wore his helmet, motorists passed 3.273.27 inches closer to him, on average, than when his head was bare. what is the whowho in this study? that is, identify the cases under study.
a. the bike riders
b. each instance of a car passing a rider
c. bike helmets
d. the cars

In this case study we have following groups:

1. Population: It had all the cars which passed the bicyclist. Out of which 3000 cars were taken.

2. Who:  Each instance of a car passing a rider, means the drivers passing by.

That is the 3000 cars which passed the researcher on his bicycle.

3. What: The distance at which cars pass the bicycle rider. The distance the drivers stayed away from his bike.

answer:

it is general formula that is used to write value to its excet position

a11 a12 a13

a21 a22 a23

it is the example of order 2 by 3 matrix in this

a11 means value occur in 1 st row 1st column

a12 means value occurs in 1st row 2nd column

a13 means value occur in 1st row and 3rd column

a21 means value occurs in 2nd row and 1st column

a22 means value occurs in 2nd row and in 2nd column

a23 means value occurs in 2nd row and in 3rd column