hello, could someone please check my statistics work? also, could you tell me the purpose of sample variance and standard deviation? as in, what they show or apply to in the data. thank you.

Question

amistre64 · Answer

variance is the square of the deviation

amistre64 · Answer

deviation tells us how wild a data set is, it is either calm and closely packed, or widely spread out and all over the place

anonymous · Answer

$$S^2 = (22.5^2 - (22.5^2/30))/30-1$$

anonymous · Answer

16.875?

amistre64 · Answer

i assume theres a data set you are working with?

anonymous · Answer

yes

amistre64 · Answer

can you post it?  or a screenshot/pic?

anonymous · Answer

yeah, hold on

amistre64 · Answer

$$var(x)=\frac{\sum(x-\bar x)^2}{N-1}$$
$$s=\sqrt{var}$$

anonymous · Answer

how do you extract an observation from that result, though? what am i looking for in terms of variance or deviation, respectively?

anonymous · Answer

attachment

amistre64 · Answer

i see you did a stem and leaf, and the data appears to be of a normal distribution.  high in the middle and small at the ends, and symmetric

anonymous · Answer

so what does that say about the deviation?

anonymous · Answer

actually i just noticed in my notes that my professor says the standard deviation is the square root of the variance...ack what am i mixed up with

amistre64 · Answer

variance is a self serving number, it is the sum of the squared distances from the mean.