SRP staff provides advice on sampling methodology and sample size to meet study objectives and budget.  Services include in-house development of specialized sample frames, or consultation with commercial sampling firms to obtain an appropriate sample.  Examples of the types of samples provided include:

• Random digit dialing (RDD) samples:  particularly suited for telephone surveys of the general population, randomly selected computer-generated telephone numbers, including both listed and unlisted, are used to target specific geographic areas.   RDD sampling for any region of the United States is available (e.g., county, state, MSA, national).  SRP uses software to draw RDD samples in-house, and also has the capability to target areas with particular demographic characteristics (e.g., ethnic and racial minorities; low/high income households).
   
• Targeted/listed samples:   samples to reach specific subgroups or rare populations.  These are useful for telephone recruitment of participants for larger studies.  They are also used for supplementing RDD samples with over-samples of rare populations.  SRP can also assist in developing or updating study-specific population lists.