In a multi-family housing assessment, how many components of a given type must be tested to obtain a desired level of confidence in results?

In a multi-family housing assessment, how many components of a given type must be tested to obtain a desired level of confidence in results?

• A. 20
• B. 60
• C. 40
• D. 80

Answer: (A)

To achieve a reliable level of confidence in the results, you need a sufficient sample size for the components being evaluated. For a multi-family housing assessment, testing a practical minimum of 20 components of a given type provides a representative snapshot of that type across the building and reduces the chance that the results are skewed by a small, unrepresentative subset. This size balances the need for accuracy with the effort required to sample. If you test fewer than 20, the sampling error can be higher, making results less reflective of the true condition across all components of that type. Testing more than 20 can improve precision, but the gains become smaller relative to the extra effort, so 20 is typically the recommended baseline. If the total number of components of that type is fewer than 20, you would test all of them.

To achieve a reliable level of confidence in the results, you need a sufficient sample size for the components being evaluated. For a multi-family housing assessment, testing a practical minimum of 20 components of a given type provides a representative snapshot of that type across the building and reduces the chance that the results are skewed by a small, unrepresentative subset. This size balances the need for accuracy with the effort required to sample.

If you test fewer than 20, the sampling error can be higher, making results less reflective of the true condition across all components of that type. Testing more than 20 can improve precision, but the gains become smaller relative to the extra effort, so 20 is typically the recommended baseline. If the total number of components of that type is fewer than 20, you would test all of them.