Science Buddies: "Ask an Expert"

our research was about comparative analysis on local beverages, and our bleep used bacterial count, isolation and etc. our professor implied that we use Mean, Median and Mode for quantitative analysis. What is the use of getting the mean median mode? thanks hope i can get an answer

Hi,

Statistically, the mean and standard deviation are the most important values for analyzing your data. The median and mode may be useful when your sample population is very large, but for lab experiments where the number of readings may only be three, the mean is what is reported. For statistical comparisons of control and experimental groups, use either standard deviation or standard error of the mean. There are websites that will calculate these for you based on your data or you can use a graphing program like Excel or SigmaPlot.

If you more questions about data analysis, let me know.

Sybee

thank you

Hi SciB, after getting the SD and mean we can use this sets of numbers into what? I mean what is the ise of getting the values? Very sorry because our professor didn't tell us exactly what is the use of getting such values and where to use them. Thanks

Hi,

Statistically speaking, the more times you repeat a reading or experiment, the more likely that your results will be accurate. Notice that i didn't say CORRECT. The truth of scientific findings depends on the way an experiment is done and by the number of times and ways that it is performed by many different people.

OK. That is why you did an average of at least three readings.

Now, the standard deviation is a measure of how close the individual readings are to the mean. So, the SD gives you confidence [or not] in your data.

You should go to Youtube and watch a couple of videos on basic statistics and the tests for comparison of two data sets. It doesn't have to be a super technical lecture. You just want a basic understanding of how to use SD. I could try to explain it to you but it would be easier for you to watch some videos with illustrations so you can understand it better.

What I do when i am graphing data is to plot the means and then add what are called error bars. These are just what they sound like--bars that you put on the chart above and below the dot that represents the mean. Your graphing program can add them once you figure out where the commands are. Just do a search for "add error bars" and you will find the info you need.

There is another measure of confidence similar to SD and that is called the standard error of the mean or SEM. I use that more often than SD for graphing data. Here's one example of how to calculate standard error but there are many more:

https://www.youtube.com/watch?v=aBXJnvQ6KFk

Hope this does it for you. If you have more questions, we'll be here...

Sybee

THANK YOU VERY MUCH SYBEE!!!!!

You ARE welcome!

Good luck...

Sybee