stratified sample?

Question

hey can someone explain in a simple way what a stratified sample is please because i really dont understand

Answer 1

Hi Gemma. A stratified sample is just a way of making sure you get a fair representation of a population. If, for example, you wanted to form a school committee of ten from 90 girls and 10 boys then you would want to make sure you had more girls in the committee than boys - wouldn't you?
Stratified sampling is all about ratio.
90 girls 10 boys
girls:boys is 90:10 or 9:1
For every 9 girls you have 1 boy so the committee would consist of 9 girls and 1 boy.
Now read your text book to see if it makes more sense.
Good luck

Answer 2

In a stratified sample the entire population of your study is broken down into different groups of strata. You then select a smaller sample, yet the ratio of the groups must be the same in the sample as in the total population.
e.g.
If you have a total population of 1000, and 400 are males. Males make up 40% of the total population.
In your sample therefore, 40% must be male. So in a sample of 100, 40 will be male.

Answer 3

Stratified Sampling

In a stratified sample the sampling frame is divided into non-overlapping groups or strata, e.g. geographical areas, age-groups, genders. A sample is taken from each stratum, and when this sample is a simple random sample it is referred to as stratified random sampling.

Answer 4

Instead of taking all the items you could sample from as one big group, you split it into smaller groups first (as long as they don't overlap) and take samples from within each one.

For example, instead of taking a sample from all the people in a cinema, you could split them up and take samples of...men aged under 18, of women in their 20's, of women in their 30's, of single men in their 20's, married men in their 20's etc etc.

It can be useful to make sure you have enough of any one particular group so you can make conclusions about them. It is also necessary if you want to make comparisons between groups.

Hope this helps.

Answer 5

But it's systematic...