(00:10)You should know by now what's great about engineer's they solve problems.
 
(00:14)All kinds of problems.
 
(00:16)I know when we think of engineers we think of big problems like crossing gorges but consider things we use every day to solve little problems.
 
(00:25)You probably remember that one of the steps of the engineering process is testing proposed solutions and 
 
(00:30)engineers always approached testing with a plan so let's check it out and see what steps engineers take to test solution.
 
(00:37) Take it away slingshot Catbot.
 

 
(00:43) A few episodes ago Catbot helped us play a game in which our problem was to try to knock down a big pile of fluffy marshmallow.
 
(00:49)We decided that we could change one of two variables to accomplish this goal. 
 
(00:54)Either how hard we pulled on the slingshot or the angle of the slingshot.
 
(00:58)So we stayed by making our best guess at both variables and missed the marshmallows completely. 
 
(01:04)The angle and how hard we pulled on the slingshot where the variables that made up our first trial
 
(01:09)When we missed the pile of marshmallows, we needed a new plan
 
(01:12)So we decided to change the angle of the slingshot and we also make sure we didn't change how hard we pulled on the slingshot.
 
(01:19)We said that we should only change one variable at a time. 
 
(01:22)Otherwise, we wouldn't be able to tell why our solution worked or didn't work. 
 
(01:25)Although we didn't know it, then this is called isolating a variable. 
 
(01:29)We're choose one variable and giving it a chance to be in the spotlight.
 
(01:33)We choose it and it alone to change between trials
 
(01:37)So we chose a new angle and started the next trial, and this trial was successful. 
 
(01:42)Down went the pile of fluffy marshmallows.
 
(01:45)Officially we can now say that we met the criteria for a successful test.
 
(01:48)Criteria are rules that are used to judge something.
 
(01:51)In this case, our criteria for a success were that we: A) Knocked over every single marshmallow 
 
(01:56)and B) did it all in one shot. 
 
(01:58)Let's see if we can name those things in another day. 
 
(02:01)I mean an investigation.
 

 
(02:06)Catbot you get to be the cheering section on this one
 
(02:09)Little Sabrina, you're up.
 
(02:10)In this game, we're going bowling. 
 
(02:12)We'll say that the criteria for success are A) knocking down the pins and B) doing it all in one turn. 
 
(02:17)That is getting a strike. 
 
(02:19)Now what are some of the variables we could change
 
(02:21)Well, 
 
(02:22)we can change how hard we throw the ball
 
(02:24)and the angle that we throw it 
 
(02:25)and the mass of the ball itself. 
 
(02:27)Just to name a few.
 
(02:28)So the next step is to isolate one variable to change between trials 
 
(02:32)So how do we go about doing that?
 
(02:34)Let's sat we choose the angle at which we throw the ball
 
(02:37)To isolate this variable, we have to make sure that all of the other possible variables stay the exact same.
 
(02:43)How can we make sure that the mass of the ball is same?
 
(02:45)That one is easy; we will just use the same ball every time. 
 
(02:48)Bam! Done! 
 
(02:49)How about making sure that we keep the speed of the ball the same. 
 
(02:52)Well that's harder, I could just do my best to throw it down the lane the exact same way every time. 
 
(02:57)Catbot, you measure the speed, Ok?
 
(02:59)My first throw was about 24 kilometers per hour. 
 
(03:02)Not too shabby, let me try again. 
 
(03:05)Hmm, my second throw was only about 22 kilometers per hour, maybe third time is the charm. 
 
(03:09)Yikes. That one was 21 kilometers per hour and my arm is getting tired.
 
(03:14)Although my three values close they're not the same and that means that another variable the speed of the ball would change during every trial.
 
(03:21)But we want our isolated variable to be the angle of the ball rolls down the lane
 
(03:26)So how else can we keep the speed the same? 
 
(03:28)What if I hard a few friends come along. 
 
(03:29)If I had some help my arm wouldn't get as tired, 
 
(03:32)but then that would introduce other variables. 
 
(03:35)My friends are all really different. 
 
(03:36)which is awesome, but not so good when it comes to trying to keep a variable constant
 
(03:41)Because my friends are different heights and, have different skills.
 
(03:44)It's not very likely that they'll roll the ball the exact same speed as I do. 
 
(03:48)So that idea is out. 
 
(03:50)I know to help us out we will use a ball ramp.
 
(03:52)All I have to do is put the same ball on the ramp each time and let gravity do the work. 
 
(03:57)Variable isolation accomplished.
 

 
(04:04)So engineers set criteria, or rules  when they're deciding if a solution to a problem is successful. 
 
(04:10)and to really know if a  solution meets these criteria they have to isolate or choose only one variable
 
(04:16)Next time we'll see how they change that variable and only that variable between trials to test the solution thoroughly. 
 
(04:22)If the solution meets the criteria, it's possibly on the path to being a huge success. 

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