Science Buddies: "Ask an Expert"

My science fair project is due on Friday. I have done the project six times, but I cannot come to a conclusion about my data. What I do is, take 3 SPF's of sunscreen and apply a thin layer onto a piece of plastic wrap. But now, I have realized, that all of my results are the same, and so is the average. I need to make a chart by FRIDAY!!! Please help The project is from science buddies

Hello courtzebra5678,

Thank you for your question. I am sorry to hear your confusion in your results--that must be really frustrating! I will try to help you as best as I can in the limited amount of time we have before Friday

Is this the project you are doing?
https://www.sciencebuddies.org/science- ... #materials

In this project your control, that is, the plastic wrap without any sunscreen on it, should have given you a UV index number. What was that number? The CONTROL is the part of the experiment in which you do not test anything--this gives you a baseline, so you know if you are getting valid results are not. Your control UV and test UV numbers should not be the same. Are they? Are any of the results a higher UV rating than the control?
Here is a good website to check out:
http://www.epa.gov/sunwise/doc/what_is_uvindex.html

1. For instance, if the UV index in the sun (as the project suggests) is 5--this will be your control-you should repeat the control every time you are planning on conducting the experiment, on the same day and time.
2. Next, you apply the sunscreen to a different piece of plastic wrap, let it dry (and making sure you follow the procedure), and take the UV reading putting the plastic over the sensor. Let's say that number is 5. That is the same number as the control! Try your other two sunscreen samples--let's say they also read a UV index of 5. There must be something wrong with the procedure, that is giving you the same value as the control. This is ok. This is exactly what the control is for! It tells you if your results are valid or not.
3. But, lets say your sunscreen sample #1 gives a reading of 5, but sample #2 gives a reading of 4. Well those are different, and you can conclude that sample #1 is not as effective as sample #2 (because you compare to the control, which gives you your baseline reading).

This project suggests doing 3 cycles of experiment, so you should have: 3 squares of each of control, sample #1, sample #2, sample #3.
If you have time, you can perform the experiment again against your control.

Remember that your control, samples 1, 2, 3 must be performed on the same day, same time for you to be able to compare the results.

So given all that, what could go wrong? Here are some ideas:
-You measured controls and samples on different days (which would change the UV number)
-The measurement of the samples were taken when the sunscreen wasn't fully dried yet
-The UV monitor is not sensitive enough to measure small differences in UV
-The calculation to figure out UV rating was done incorrectly


And, how do you finish the project?
--First, report the actual results that you did get (don't ever fudge on the data, in the real world you can get into BIG trouble for that). It's okay if they don't make sense to you.
--In your discussion of your results, talk about how you performed the procedure and if you thought that you may have made a mistake in any of the steps, or if you noticed anything interesting or unexpected in the results. Your discussion will be analyzing your results, but since all of your control and test samples had the same values, your discussion will be about this and what you think you could do next time to get different results. Some questions to consider and answer in your discussion/ conclusion are:
1. Why do you think you got the results you did?
2. How would you perform the next experiment and what would you change?
3. What were you expecting the results to be based on your research?

One thing to remember is that results like this do happen, even to professionals, and we have a hard time explaining why--but this is why it is important to keep detailed lab notebooks so we can analyze our results and to do further research to try and explain why we are seeing what we are seeing.

Hope that helped. Let me know how it goes!

Ok, so I did the project 6 times. Most of the time, except for once or twice, the UV index was 2. My readings for the pieces of plastic with the sunscreen were only 1's or 0's, and for the most part, everytime I conducted the experiment, my indexes for each plastic with sunscreen was 1 or 0. Is it because it is the winter, and the sun as strong? Thanks for all the help though!!!!

what should I do? I need to make a chart asap!!!

Hello,
Thank you for the detailed information! Good job! It sounds like you do have some varied results from the control-so that is good. So I assume that when you say:

courtzebra5678 wrote:Most of the time, except for once or twice, the UV index was 2

, you mean that your CONTROL was 2? The control is the UV index without sunscreen (just the plastic wrap). The fact that with your experimental sunscreens the UV reading was 0 or 1 is good---that means the sunscreen works and decreased the UV exposure. Why is it important to know that your control gave a UV index of 2, and your TEST sunscreen gave a reading of 0? What is the significance of that? You will put your answer in your conclusion. In your report you will restate your hypothesis (what you thought would happen) and discuss your results and make a conclusion. Here are some resources on how to do that:
https://www.sciencebuddies.org/science- ... ions.shtml

You are right in that, because it is winter (and I do not know the part of the country you live in), and there are more clouds, the results will not be the same as if it were the middle of summer. This is something you will want to talk about in the DISCUSSION part of your paper.
https://www.sciencebuddies.org/science- ... port.shtml

For the results section, you will need to have a chart: https://www.sciencebuddies.org/science- ... ysis.shtml.
You can use a spreadsheet format. If you really did 6 unique experiments, then you will have samples 1-6, rather than samples 1-3.
It will look something like this:

Test: should have been same day/time/conditions, etc.
Control 1, 2, 3: UV index #
Sunscreen Sample 1 (3 separate samples) :UV index# 1, 2, 3= take the average of 1, 2, and 3
Sunscreen Sample 2 (3 samples) : UV index# 1, 2, 3= take the average of 1, 2, and 3
Sunscreen Sample 3:UV index# 1, 2, 3= take the average of 1, 2, and 3

Results:
Control 1-Average of Sample 1
Control 2-Average of sample 2
etc.


You dont have to have it set up the way I did, you just want to make sure the data is clearly laid out and that you know what you are doing. You will be comparing your samples to the control. For how to do your calculation, you will take the average (read the procedure for details) of each Sample sunscreen. https://www.sciencebuddies.org/science- ... #procedure.
Also review: https://www.sciencebuddies.org/science- ... ianandmode
Here is a resource to check against your results. You can use this resource in your results: are they consistent with your findings/readings for UV?
http://www.weather.com/maps/activity/sk ... =undefined

Hope that helped. I will do my best to help you before Friday. I definitely think you can rock this!

ok thanks so much! I will let you know how Friday goes. As for my graphs, I made bar graphs showing how the index remained the same, and I learned that my checker only measures in whole numbers, so that was probably why my results were the same. I made another graph of the irradiance, and from that information, I was able to determine that the SPF 30 worked the best.
Thanks again for all the help, and I hope that I wasn't a pain, but as I said, I will let you know how Friday goes.

Hello!

Great-sounds like you nailed it and came up to some good conclusions. You are right in that sometimes we have to look at different sets of information (the irradiance) in order to analyze the data, but you did an excellent job at pooling your resources. Good job. I can't wait to hear how it turns out!
I am curious to know if you used sunscreens with SPF over 30? I definitely need a high SPF protectant in the summer, since I burn easily,

Happy Friday