Hello all(adsbygoogle = window.adsbygoogle || []).push({});

This is not homework, i work in engineering.

I have some data in a table, there are 3 columns and 5 rows.

The data relates to how high or low one rail is to the other.

The data was collected across 3 days. At each 7m intervals the height of the right hand rail was measured against the left hand rail.

The objective was to determine if the rails were moving up or down from each other and then to calculate if that movement was severe.

After calculating the mean, variance and SD, I can say that;

at each position there was 2 x data points within 2 x SD of the mean and 1 x data point within 1 SD of the mean and 0 x data points within 3 SD of the mean.

But what does this mean, how do you interpret the data, what is the data telling me in context of my example???

I know that if all of my data points was within 1 SD of the mean then would that indicate that there is little movement between the rails at each position.

After looking at the data & the SDs would you say that between 0 – 28m there is lots of movement or little movement & how can you quantify this interms of a percentage for exameple.

Attached is the data I am using.

Thank you for your help.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# A little help understanding standard deviation & variance

**Physics Forums | Science Articles, Homework Help, Discussion**