Hey there! Sign in to join this conversationNew here? Join for free
 You are Here: Home >< A-levels

# Standard Deviation? Watch

1. How do you work out the standard deviation from these three pieces of data?

Replicate 1: 725 Replicate 2: 699 Replicate 3: 824
2. Here's how they found the first one, now have a go yourself at the missing one

Although this is not a maths paper so I don't know what they're expecting you to do - do you have a cassio with stats mode? You can work it out very quickly on there.
3. I'm going to use the example for the first row since the numbers are all there.

1) Calculate the mean of the values which is 328.0

2) subtract the mean from each individual data set.
So 324-328.0=-4
362-328.0= 34
298-328.0= -30

3) square each of the values to get rid of any negatives
So -4^2 is 16
34^2 is 1156
-30^2 is 900

4) total up the squared numbers
This was 2072

5) you then divide the total of numbers by n-1 (where n is the number of values)
2072/2= 1036

6) to get to the final value, simply square root the answer above which equals to 32.2 when rounded to one decimal place.

This conforms to the standard deviation formula the user above posted.

Try this for the second row now.
4. (Original post by QPRTeags)
Here's how they found the first one, now have a go yourself at the missing one

Although this is not a maths paper so I don't know what they're expecting you to do - do you have a cassio with stats mode? You can work it out very quickly on there.
Thanks, that was very helpful. I got 66.523, which I think is correct. This is from a practice Biology paper to prepare me for my exam next Wednesday. Thanks to you I may just pass. Or, at least get a question like this correct in my exam!
5. (Original post by aamirac)
I'm going to use the example for the first row since the numbers are all there.

1) Calculate the mean of the values which is 328.0

2) subtract the mean from each individual data set.
So 324-328.0=-4
362-328.0= 34
298-328.0= -30

3) square each of the values to get rid of any negatives
So -4^2 is 16
34^2 is 1156
-30^2 is 900

4) total up the squared numbers
This was 2072

5) you then divide the total of numbers by n-1 (where n is the number of values)
2072/2= 1036

6) to get to the final value, simply square root the answer above which equals to 32.2 when rounded to one decimal place.

This conforms to the standard deviation formula the user above posted.

Try this for the second row now.
Thanks, this was very helpful!
6. (Original post by doitforyou)
Thanks, that was very helpful. I got 66.523, which I think is correct. This is from a practice Biology paper to prepare me for my exam next Wednesday. Thanks to you I may just pass. Or, at least get a question like this correct in my exam!
Yes, 66.5 is correct, well done!

No problem, good luck in the exam!

Reply
Submit reply
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: June 2, 2016
Today on TSR

### 'Entry requirements are a form of elitism'

What do you think?

### Should I judge my gf for this?

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Help with your A-levels

## All the essentials

### Student life: what to expect

What it's really like going to uni

### Essay expert

Learn to write like a pro with our ultimate essay guide.

### Uni match

Our tool will help you find the perfect course for you

### Create a study plan

Get your head around what you need to do and when with the study planner tool.

### Resources by subject

Everything from mind maps to class notes.

### Degrees without fees

Discover more about degree-level apprenticeships.

### Study tips from A* students

Students who got top grades in their A-levels share their secrets

## Study help links and info

Can you help? Study help unanswered threadsRules and posting guidelines

## Sponsored content:

### HEAR

Find out how a Higher Education Achievement Report can help you prove your achievements.

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.