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# Am I in a Cluster Sample, like In SaS Procedures?

Hi EveryBody,

I am working on a survey, and i am tring to see how can I use SAS for estimate Standard error and some of other statistics. I read a lot of things about that, and have concluded that the first thing, and probably the most important thing to do

is to determine wich design my survey is, thus i can use sas procedures.

What i need from you, if possible is :

1- confirming if this is correct :

I am sampling Housholds and after that interviewing all members of each of these households-----> So this is a one-stage Cluster sampling. IS THAT CORRECT?

2- if I am true in -1- then how can i use proc surveymeans etc..

Just tell SAS that CLUSTER is my Household variable ? and what else?

Thanks a lot

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Solution
‎01-15-2015 05:56 AM
Contributor
Posts: 57

## Re: Am I in a Cluster Sample, like In SaS Procedures?

Sorry, I didn't include that in my first response.  Yes, you will specify the total number of households in the population in the proc surveymeans like this:

proc surveymeans data=yourdata total=NumberOfHouseholdsInPopulation;

cluster Household;

var age;

weight YourFinalSampleWeight;

run;

Your weight is the inverse of the probability of selection of of a household, since you are taking all household members into your sample.  So if you sampled 20 households out of 200, your weight would be YourFinalSampleWeight=1/(20/200)=10.

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Contributor
Posts: 33

## Re: Am I in a Cluster Sample, like In SaS Procedures?

Am I in the right place for my question, if not, please show me where to post it.

Thank you.

Contributor
Posts: 57

## Re: Am I in a Cluster Sample, like In SaS Procedures?

Yes, it sounds like you have a cluster sample going on here, but it's difficult to tell without more information.  As long as you have performed a simple random sample of households in your population and have not stratified first (e.g. drawn households separately in rural and urban areas, for example), then what you have is a single stage cluster sample.  Let's say you were trying to estimate the average age.  Then in SAS, you would issue the following commands:

proc surveymeans data=yourdata;
cluster Household;
var age;
weight YourFinalSampleWeight;
run;

where YourFinalSampleWeight is the variable in your dataset that contains the value of the final sample weight for the individual, which in this case would be the inverse probability of selection, assuming you are not making any non-response or post-stratification adjustments.

Best of luck!

Contributor
Posts: 33

## Re: Am I in a Cluster Sample, like In SaS Procedures?

Thanks a lot for your respose Statistician13,

Effectively it seems to be a one stage sampling because I slect all members of the households. and I can't do anything now about changing the design, the survey will be acheived soon, and my work is to get standard error, confidence interval etc...

Here I have 2 more questions:

1- Have I to tell SAS the _TOTAL_ of households in my frame population or sampling rate (if the total is not available)?

2- for the weights is the weight of my households MEMBERS.

for information ,yes, I have non-response adjustments.

Thanks

Solution
‎01-15-2015 05:56 AM
Contributor
Posts: 57

## Re: Am I in a Cluster Sample, like In SaS Procedures?

Sorry, I didn't include that in my first response.  Yes, you will specify the total number of households in the population in the proc surveymeans like this:

proc surveymeans data=yourdata total=NumberOfHouseholdsInPopulation;

cluster Household;

var age;

weight YourFinalSampleWeight;

run;

Your weight is the inverse of the probability of selection of of a household, since you are taking all household members into your sample.  So if you sampled 20 households out of 200, your weight would be YourFinalSampleWeight=1/(20/200)=10.

Contributor
Posts: 33

## Re: Am I in a Cluster Sample, like In SaS Procedures?

Great.

And the sampling method of the households doesn't have an impact on my SAS procedure, in other words, is it the same syntax if sampled my households by a SRS or any other method?

Contributor
Posts: 57

## Re: Am I in a Cluster Sample, like In SaS Procedures?

I'm not sure I fully understand your last questions.  The sampling rate of the households will be taken into account when you calculate the rates.  You will need to add the CLUSTER statement to your SAS code, so it's not the same as SRS Code.

Contributor
Posts: 33

## Re: Am I in a Cluster Sample, like In SaS Procedures?

this is what i mean :

for instance for this two possibilities  of my cluster sampling :

1 -  First sampling the households(clusters) with a simple random sampling and after that select all members of the households.

2 -  First sampling the households(clusters) with a probability sampling size and after that select all members of the households.

are this two possibilities the same for SAS procedure, i don't have to tel him that i user a simple random sampling for my clusters?

i hope I am more clear now.

thank you

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