You are Here: Home >< A-levels

# Can someone please explain these questions to me? (Biology A2)

1. Explain why it might sometimes be more appropriate to use systematic sampling? (3marks)

A microscope slide of human blood may contain thousands of red blood cells, how could you use random sampling to estimate the number of cells in 1cm3 of blood (4 marks)
2. Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

Just quoting in Danny Dorito so she can move the thread if needed
Spoiler:
Show
(Original post by Danny Dorito)
x
3. (Original post by Weronika_m)
Explain why it might sometimes be more appropriate to use systematic sampling? (3marks)

A microscope slide of human blood may contain thousands of red blood cells, how could you use random sampling to estimate the number of cells in 1cm3 of blood (4 marks)
1. Systematic sampling is when samples are taken from a large population in relation to a fixed point. This may be more appropriate where there are limits on time, money and resources for the investigation.

2. Split the slide into a grid and use a number generator to select 3 random 1cm^3 coordinates. Count the blood cells in those coordinates and find an average. Repeat this 3 times, keeping the source, thickness and microscope the same.

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: September 26, 2016
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:
Today on TSR

### How hard is work at Oxbridge?

Is it really that intense? Would I cope?

Poll

## 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.

### 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.

### Study tips from A* students

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