statistics question

Question

Tell if each variable is continuous or discrete.

 

a. Tonnage carried by an oil tanker at sea.

b. Wind velocity at 7 o’clock this morning.

c. Number of text messages you received yesterday.

Answer 1

A discrete variable is one that has to be an exact number of something and cannot just continue "along a straight line."  A good example is the number of people - you cannot continue along a line, hit the 6th person, and be partway towards a 7th person.  You either hit 7 or you don't.  Other examples are days in a month, the number of dogs you have, the number of tests your class will have, etc.

 

Continuous is something that can go along a straight line and be any number in between, and could just continue along that line.  Examples would be linear measurements, temperatures, time.  For example, in comparison to the people, if it were 6 degrees out, the temperature doesn't just jump suddenly to 7 degrees - it will continue along a line, hitting an infinite number of points in between.  Note that being difficult to measure slight increments is not relevant.  That is, it might be difficult for a normal person to measure something smaller than a millimeter on a ruler, but measurements in between those millimeters do exist, or the thermostat might only measure to one decimal point, but points in between do exist. 

 

So the easiest way to tell is to ask yourself if there's a number in between that can exist.  If you have two temperatures of 6.001 degrees and 6.002 degrees, is it possible for it to be in between?  Yes, it can be 6.0015 degrees. :-)  If you have 6 people and 7 people, is it possible for there to be something in between?  No.

 

See how well you can answer those 3 now. :-)