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So, variables. There are lots of them when trying to test an idea. The trick is to isolate one variable at a time to get reliable results every time. But, how do we do that? In this episode of Crash Course Kids, Sabrina shows us how to isolate variables at the bowling alley!

///Standards Used in This Video///
3-5-ETS1-3. Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

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Producer & Editor: Nicholas Jenkins
Cinematographer & Director: Michael Aranda
Host: Sabrina Cruz
Script Supervisor: Mickie Halpern
Writer: Jen Szymanski
Executive Producers: John & Hank Green
Consultant: Shelby Alinsky
Script Editor: Blake de Pastino

Thought Cafe Team:
Stephanie Bailis
Cody Brown
Suzanna Brusikiewicz
Jonathan Corbiere
Nick Counter
Kelsey Heinrichs
Jack Kenedy
Corey MacDonald
Tyler Sammy
Nikkie Stinchcombe
James Tuer
Adam Winnik

 (00:00) Crash Course Kids Intro

(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.

 (00:39) Big Question Intro

(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.

 (02:02) Investigation Intro

(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
(02:22)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.

 (04:00) Conclusion Intro

(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.