standard deviation a level maths

Why does standard deviation double if all the data values were halved? I thought the standard deviation would halve too?

Reply 1

mqb2766

Original post by cloverleaf39

Why does standard deviation double if all the data values were halved? I thought the standard deviation would halve too?

Youd have to post the question / working youre referring to as if the data values are halved, then the standard deviation would half as well.

Reply 2

cloverleaf39

this is just from notes I wrote in class, I was just unsure if I had written it down wrong

Original post by mqb2766

Youd have to post the question / working youre referring to as if the data values are halved, then the standard deviation would half as well.

Reply 3

mqb2766

Original post by cloverleaf39

this is just from notes I wrote in class, I was just unsure if I had written it down wrong

Sounds like it. For linear coding so x -> ax + b, the mean is increased by b (mu -> mu+b) and the std dev is scaled by a (sig -> a*sig)
https://www.youtube.com/watch?v=QpfDlCPDOKQ
Its fairly intuitive if you sketch the data/distribution, but the relationships drop out of the definitions fairly easily.