# Maths!

WatchThis discussion is closed.

Report

#2

(Original post by

Hi

How do you carry out standard deviation?

thanx!

**CHAD**)Hi

How do you carry out standard deviation?

thanx!

i.e. sdÂ²=mean[(x-mean(x))Â²]

0

(Original post by

you work out the mean of all your numbers. you take the mean away from all those numbers, and square these new numbers. you then work out the mean of this new set of numbers, then squareroot it.

i.e. sdÂ²=mean[(x-mean(x))Â²]

**elpaw**)you work out the mean of all your numbers. you take the mean away from all those numbers, and square these new numbers. you then work out the mean of this new set of numbers, then squareroot it.

i.e. sdÂ²=mean[(x-mean(x))Â²]

What would you use standard deviation to prove?

0

Report

#4

(Original post by

What would you use standard deviation to prove?

**CHAD**)What would you use standard deviation to prove?

for example {-1,0,1} and {-100,0,100} have the same mean, but the second one has a higher sd because it is more spread out

0

(Original post by

its not really used to prove anything, the same way the mean doesnt prove anything. its just a way of measuring how spread-out the data is.

for example {-1,0,1} and {-100,0,100} have the same mean, but the second one has a higher sd because it is more spread out

**elpaw**)its not really used to prove anything, the same way the mean doesnt prove anything. its just a way of measuring how spread-out the data is.

for example {-1,0,1} and {-100,0,100} have the same mean, but the second one has a higher sd because it is more spread out

right, so if the answer 4 the standard deviation was 24.7, what would you say?

0

Report

#6

(Original post by

right, so if the answer 4 the standard deviation was 24.7, what would you say?

**CHAD**)right, so if the answer 4 the standard deviation was 24.7, what would you say?

0

(Original post by

what can you say? it depends on what data you have.

**elpaw**)what can you say? it depends on what data you have.

k. so say I had the data for the BMIs for 13 female students in year 7 and the standard deviation thingy answer was 24.7 wot wud I say?

0

Report

#8

The standard deviation figure (in this case 24.7) shows that 68% of the data lies 24.7 units either side of the mean. Which if you're looking at BMIs suggests a wide spread. So wide that I'd try and calculate it again.

0

Report

#9

(Original post by

k. so say I had the data for the BMIs for 13 female students in year 7 and the standard deviation thingy answer was 24.7 wot wud I say?

**CHAD**)k. so say I had the data for the BMIs for 13 female students in year 7 and the standard deviation thingy answer was 24.7 wot wud I say?

0

(Original post by

The standard deviation figure (in this case 24.7) shows that 68% of the data lies 24.7 units either side of the mean. Which if you're looking at BMIs suggests a wide spread. So wide that I'd try and calculate it again.

**XTinaA**)The standard deviation figure (in this case 24.7) shows that 68% of the data lies 24.7 units either side of the mean. Which if you're looking at BMIs suggests a wide spread. So wide that I'd try and calculate it again.

I just made the number up. but if it was the number and the mean was say 30, half the data wud be up to 24.7 units below it and the other half of the data would be up to 24.7 units above it? right? So if this were true, I would say that there is an immense variation in the bmi's of female students in year 7?

0

Report

#11

(Original post by

I just made the number up. but if it was the number and the mean was say 30, half the data wud be up to 24.7 units below it and the other half of the data would be up to 24.7 units above it? right? So if this were true, I would say that there is an immense variation in the bmi's of female students in year 7?

**CHAD**)I just made the number up. but if it was the number and the mean was say 30, half the data wud be up to 24.7 units below it and the other half of the data would be up to 24.7 units above it? right? So if this were true, I would say that there is an immense variation in the bmi's of female students in year 7?

0

Report

#12

(Original post by

Hi

How do you carry out standard deviation?

thanx!

**CHAD**)Hi

How do you carry out standard deviation?

thanx!

0

(Original post by

No, 34% lies 24.7 units below, 34% lies above. The smaller the figure, the less the spread.

**XTinaA**)No, 34% lies 24.7 units below, 34% lies above. The smaller the figure, the less the spread.

0

Report

#14

(Original post by

sooooo how do you know it is 34%????

**CHAD**)sooooo how do you know it is 34%????

0

Report

#15

(Original post by

sooooo how do you know it is 34%????

**CHAD**)sooooo how do you know it is 34%????

0

(Original post by

At GCSE you just take it as a given. You may find out at A-Level when you study the normal distribution in S1...

**XTinaA**)At GCSE you just take it as a given. You may find out at A-Level when you study the normal distribution in S1...

is it always 32% then?

0

Report

#18

(Original post by

is it always 32% then?

**CHAD**)is it always 32% then?

0

Report

#19

(Original post by

is it always 32% then?

**CHAD**)is it always 32% then?

(assuming data is normally distributed)

0

Report

#20

(Original post by

yes, always 68% of the data lies within + or - the sd of the mean

(assuming data is normally distributed)

**elpaw**)yes, always 68% of the data lies within + or - the sd of the mean

(assuming data is normally distributed)

0

X

new posts

Back

to top

to top