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Random Survey Methodology Using A Random Number Generator. Michael V. Jacobs Southern Georgia Regional Commission. When To Use Random Surveys. When there are large numbers of households in the Universe such as in large area-wide benefit or city-wide benefit infrastructure projects, etc.

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random survey methodology using a random number generator

Random Survey MethodologyUsing A Random Number Generator

Michael V. Jacobs

Southern Georgia

Regional Commission

when to use random surveys
When To Use Random Surveys
  • When there are large numbers of households in the Universe such as in large area-wide benefit or city-wide benefit infrastructure projects, etc.
  • When there are more households in the Universe than the minimum sample size of 50 in a Universe of 55 or less
selecting the sample
Selecting The Sample
  • Define the group whose characteristics you are trying to estimate
  • Determine how many households in that group must be sampled in order to estimate the overall characteristics accurately
  • Make allowances for households that are not able to be interviewed (Surveys in the random sample must be completed for income level)
  • Finally, you must actually select the households to be interviewed
defining the group or universe
Defining The Group Or “Universe”
  • The large group whose characteristics you seek to estimate is called the “Universe”
  • Need to know the number of households served by the CDBG funded project(s)
  • Determine if part of your project may only benefit certain households (not an area-wide benefit) or if there are different areas of benefit in multiple budget categories
  • If so, you may need to have multiple Universes or do different types of surveys
defining the group or universe5
Defining The Group Or “Universe”
  • You could physically list residences, start with a list of connected addresses, or use a combination of both to get your base Universe list
  • You must add or delete households that will or will not benefit from the CDBG funded project
  • Delete Governmental (leave Prisons), Commercial and Industrial Customers from the list leaving only Residential Customers
defining the group or universe6
Defining The Group Or “Universe”
  • Mention all customers in the methodology
  • Identify Apartments, Nursing Homes, Dorms & Housing Authority Units in the list (which may only have one address for multiple units).
  • Delete the one address of these when appropriate (which may be an office anyway)
  • Add an addendum to your base list containing actual occupied apartment/unit addresses or numbers, available by contacting the management
defining the group or universe7
Defining The Group Or “Universe”
  • Prisons count as one address and one low-moderate income person, should they be randomly selected
  • Include each Nursing Home resident in the Universe if the administrator will complete the surveys using their income/Medicaid data, or the residents are considered able to be surveyed. This may not be possible due to HIPAA regulations/nursing home policy.
defining the group or universe8
Defining The Group Or “Universe”
  • Nursing home residents are not automatically considered low-moderate income for area benefit type surveys
  • If entirely unable to be surveyed, you might exclude them from your Universe sample, but contact DCA for alternatives first
  • Dorms should be included, but residents sampled must be adults (that is, not listed on parent’s income tax as dependents) with own income
defining the group or universe9
Defining The Group Or “Universe”
  • Be sure to mention all unique living situations in your text
  • Add to your base list addendum any households that may benefit from the project (such as fire coverage from fire hydrants) even though they may not be on the connection list
  • Add to your base list addendum any households that will be added to the connection list as a result of this project
defining the group or universe10
Defining The Group Or “Universe”
  • Assign each household on your Universe list a unique number
  • Follow up with a physical look at the area to verify numbers/addresses
determining sample size
Determining Sample Size
  • Take the total number of households on your Universe list(s) and compare to “Table 2: Required Sample Sizes for Universes of Various Sizes” in the “Guide to Acceptable Survey Methodology” for minimum sample sizes
  • You may use larger samples if all are chosen in the same manner
  • Remember these are completed surveys
households unable to be interviewed
Households Unable To Be Interviewed
  • Regardless of the random survey method chosen, you must determine how you will replace those households that cannot be surveyed
  • This could be a result of not being home 3 times, vacancies, mental impairment, etc.
  • In using a random number generator, which I recommend, you would simply move on to the next random number in your list
selecting households for interviews
Selecting Households For Interviews
  • Everyone who is on the Universe list must have an equal chance of being included in the sample
  • A random number generator is the best way to randomly select numbers from your Universe list
  • http://www.graphpad.com/quickcalcs/randomN1.cfm has a great random number generator (Refer to your handout)
selecting households for interviews15
Selecting Households For Interviews
  • Choose “Generate Random Integers”, creating a table with 1 column of however many numbers you need rows
  • Remember to choose many more numbers than your minimum sample size (Oversample) because of replacements and the fact that the chosen random numbers may repeat themselves multiple times
selecting households for interviews16
Selecting Households For Interviews
  • Randomly select each value within this range: From 1 to last number on your Universe list
  • Click “Do it!”
selecting households for interviews17
Selecting Households For Interviews
  • This will generate a list of random numbers, though some numbers may repeat themselves
  • Print and make an extra copy for your records to keep “clean”
  • Prepare your surveys by marking them with the minimum sample size needed (1-minimum)
  • Take the 1st random number, relate it to the household on your list with the same Universe number and mark their address on your survey form along with their Universe number.
  • Do this, straight down the random number list, until you have the required minimum number of surveys
  • Mark through the repeats as you come to them and make a notation to the side of each
  • If they cannot be surveyed, mark the reason why on the form and replace it with the next random number on your Universe list, but retain the form’s survey number
  • Keep a file with the “bad” surveys and record their Universe list numbers, so they are not repeated later
  • After the minimum numbers of surveys are obtained, complete the “Low and Moderate Income Survey Worksheet” found in the Guide To Acceptable Survey Methodology
special circumstances
Special Circumstances
  • Different areas of benefit either within the same budget category or in other budget categories
  • More households/addresses are found later that were not on the original Universe list
  • The area benefit contracts or expands due to a project change after the survey has begun
  • Other special circumstances