The mean shoe size of the students in a math class is 7.5. most of the shoe sizes fall within 1 standard deviation, or between a size 6 and a size 9.

what is the standard deviation of the shoe size data for the math class?

1.5

2.7

3.0

3.8

1.5

Step-by-step explanation:

The mean is the Middle number.

1 standard deviation in both sides of 7.5 makes it between 6 and 9.

What is the "common difference" in 6 to 7.5 and from 7.5 to 9?

and

So, we would say the standard deviation is 1.5

Answer choice A is right.

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.

all it means is function 3