# coureswork help please

#### miten

##### New Member
can someone please tell me what does a higher standard deviation mean? for example the suns standard deviation is 2 and the mirrors is 3
aswell what a higher mean means? and why we do a cumulative frequency graph and a normal distrubution graph.i would relly appricate it if sum1 would help me.

#### yupeh

##### New Member
Hello!
Standard Deviation measures the dispersion of your data set without the set back of having a different unit/s (since it is the positive square root of the variance). But the standard deviation has meaning only when comparing two or more sets of data having the same units of measurement and approximately the same mean. It has no meaning otherwise rather a measurement, on the average, of the difference of each data in the data set from the mean. Thus, your example above (assuming that that suns and mirrors have the same unit of measurement and same means), the mirrors are more variable that the suns. Note that standard deviation is affected by value of every observation and thus affected by few extreme values.

On the other hand, Mean is the most representative value of the distribution. It summarizes all the data in your data set into one observation though it may not exist in your data set and is affected by extreme values. High means may mean two things:
1. one, your data set has high values thus entailing high means.
2. the data in your data set may have relatively equal very low extreme values and very high extreme values thus entailing high or moderate value

hope this thoughts helps ...