Science Buddies: "Ask an Expert"

My project is on, " Determining Iodide Content of Salt." I know everything but the dependent variable. Please help me on this. What is my dependent variable for this experiment? Help ASAP !!

Hi
Dependent variable is something that you measure in the experiment, which in this case would be the amount of iodine found in each of the salt samples. Therefore, I think the dependent variable can be the percent by mass of iodine in each of the samples.

jkim77 wrote:Hi
Dependent variable is something that you measure in the experiment, which in this case would be the amount of iodine found in each of the salt samples. Therefore, I think the dependent variable can be the percent by mass of iodine in each of the samples.

How would I measure that? Can you explain how I would do that? The salt will just turn a color like purple-blue which means it has iodine.

Hello. I assume you are doing this project:
https://www.sciencebuddies.org/science- ... p011.shtml

First let's review definitions of different types of variables. More discussion can be found here:
https://www.sciencebuddies.org/science- ... bles.shtml

Controlled variable: settings you wish to keep constant in your experiment so that it doesn't affect the outcome
Independent variable: settings which you, as the scientist, change in order to see how it affects the outcome of your experiment
Dependent variable: what you measure to determine whether it is affected by your independent variable(s)

I won't directly tell you what your variables are, but let's discuss what you think your variables are by the above definitions. What are you changing during your experiment (independent variables)? What are you measuring as the outcome (dependent variables)? What are you keeping constant (controlled variables)?

Take a first attempt at your variable definitions, why you picked them, and we can go from there.

Good luck!

dcnick96 wrote:Hello. I assume you are doing this project:
https://www.sciencebuddies.org/science- ... p011.shtml

First let's review definitions of different types of variables. More discussion can be found here:
https://www.sciencebuddies.org/science- ... bles.shtml

Controlled variable: settings you wish to keep constant in your experiment so that it doesn't affect the outcome
Independent variable: settings which you, as the scientist, change in order to see how it affects the outcome of your experiment
Dependent variable: what you measure to determine whether it is affected by your independent variable(s)

I won't directly tell you what your variables are, but let's discuss what you think your variables are by the above definitions. What are you changing during your experiment (independent variables)? What are you measuring as the outcome (dependent variables)? What are you keeping constant (controlled variables)?

Take a first attempt at your variable definitions, why you picked them, and we can go from there.

Good luck!

Okay so my independent variable ( what I'm changing) is the different types of salts.
My control is going to be the positive iodine which I will be making. That's my control because that helps me whether the salts I will be testing will have iodine.
My dependent is.... I'm not quite sure on what to measure. If I chose the color which it's going to show, how will I measure that ?

Independent variable is correct.

Let's talk about your control. Almost! You aren't making iodine...you are making a solution to check for iodine. You want your solution to check for iodine to be the same when testing each salt. Therefore, your testing solution is the control variable.

So, I just mentioned that you're testing for the presence of iodine. The presence of iodine is dependent on the salt type (independent variable).

Now, what are your thoughts?

dcnick96 wrote:Independent variable is correct.

Let's talk about your control. Almost! You aren't making iodine...you are making a solution to check for iodine. You want your solution to check for iodine to be the same when testing each salt. Therefore, your testing solution is the control variable.

So, I just mentioned that you're testing for the presence of iodine. The presence of iodine is dependent on the salt type (independent variable).

Now, what are your thoughts?

Great! So for my dependent variable , how would I measure that ?

If iodine is present, your solution turns blue, correct? Your response will simply be a binomial response: iodine is present or not present.

dcnick96 wrote:If iodine is present, your solution turns blue, correct? Your response will simply be a binomial response: iodine is present or not present.

Yes but doesn't dependent means measured ? What will I measure if it only turns a color indicating iodine is presented ?

A binomial response (does it have iodine or doesn't it) IS a measurement. Think of surveys as an example. If I want to know how many people like to eat spinach, when I ask each person, they answer yes or no. When asking the question to each person, I am taking a measurement. The collection of the individual measurements will result in a percentage of people that like spinach. The statistical term for this type of data analysis is binomial regression. If you did multiple measurements for each type of salt (which you should), you can calculate your own percentages.

dcnick96 wrote:A binomial response (does it have iodine or doesn't it) IS a measurement. Think of surveys as an example. If I want to know how many people like to eat spinach, when I ask each person, they answer yes or no. When asking the question to each person, I am taking a measurement. The collection of the individual measurements will result in a percentage of people that like spinach. The drastically term for this type of data analysis is binomial regression. If you did multiple measurements for each type of salt (which you should), you can calculate your own percentages.

Ohhh!! Thank you ! I get it now. Thank you so much.

Also, about the measurements of the salt, will that also be counted as my dependent variable or should I just stay with the iodine presented ?

Thank you.

I recommend keeping the amount of each salt the same. Otherwise, different amounts of salt could affect the outcome, which makes it another independent variable. While the different salts is your independent variable, the amount of salt used can be a control variable.

I think having the one dependent variable is fine.

I'm glad you have a better understanding now. A lot of times, planning and setting up the experiment is the hardest part. Continue to write back if you have further questions. Good luck!

dcnick96 wrote:I recommend keeping the amount of each salt the same. Otherwise, different amounts of salt could affect the outcome, which makes it another independent variable. While the different salts is your independent variable, the amount of salt used can be a control variable.

I think having the one dependent variable is fine.

I'm glad you have a better understanding now. A lot of times, planning and setting up the experiment is the hardest part. Continue to write back if you have further questions. Good luck!

Hello, i'm back!
I have one last question about my experiment. I have everything ready and all I need now is the graph. I have a data table , but I dont have a graph.
Please help me before Monday, tomorrow or tuesday. Tuesday is my due date.

So basically, in my experiment we need to have both data table and a graph. Like i already have said, I have a data table and all I need is a graph.. ****I'm not sure what graph to make and what to do for the graph. The two choices for the graph is a bar or line.**** Please help. ASAP.

Hello! Congratulations on finishing your project.

A line graph is best when trying to analyze trends over time. A bar graph is best when trying to compare between groups. Which do you think is best?

The only data you have to show is whether each salt solution contains iodine or not. You could assign along the y graph a value of 1 if the salt contains iodine and a value of 0 if it does not contain iodine. This is pretty standard notation for a binomial response. Did you test each salt multiple times? If so, perhaps plot the number of times each salt tested positive for iodine.

Good luck!

Hello, I just wanted to make sure.
Why do some salts contain iodine but other salts don't?

Iodine is an important nutrient that can cause health problems if not enough is ingested on a daily basis. Iodine was introduced to salt in attempt to reduce the number of people with iodine deficiency. Not all salts contain iodine, because it is not required by the government to do so. A simple Google search will provide plenty of articles with more information about the importance of iodine and why companies began adding it to salts.

Good luck!

Oh thanks. This is what I said during my presentation.
Thanks for you help !

Excellent. Let us know how you did. Best of luck!