Section 411.310  General Characteristics of the Customer Survey

a)         The customer survey shall be conducted annually, in the fall, on the anniversary of the initial survey.

b)         The survey shall be identical for all jurisdictional entities.

c)         The survey shall be conducted for residential and non-residential customers. For the residential population, the survey respondent shall be the person in the household who is most familiar with the household's electric service. For non-residential customers, the survey respondent shall be the person who is most familiar with electric service in the organization.

d)         For each jurisdictional entity, the sample size shall be adequate to ensure that answers are reflective of the population at a specified statistical level of confidence and confidence interval as follows:

1)         For residential customers, sample size shall be sufficient to achieve a 95% confidence level with a confidence interval of ± 4.0%. This confidence level and confidence interval equates to 600 respondents for utilities with 10,000 or more residential customers. The sample size for utilities with fewer than 10,000 residential customers would be adjusted by a finite population correction factor calculated as (N-n)/(N-1), where N = population size and n = originally required sample size.

2)         For non-residential customers, sample size shall be sufficient to achieve a 95% confidence level with a confidence interval of ± 4.9%.  This level of confidence and confidence interval equates to 400 respondents for utilities with 10,000 or more non-residential customers and accordingly fewer (i.e., (N-n)/(N-1)) for smaller jurisdictional entities.

e)         Before eliminating a customer and randomly selecting a replacement, the jurisdictional entities shall:

1)         make a minimum of five telephone calls to each randomly selected customer;

2)         attempt to reach the randomly selected customer at different times of day;

3)         call the customer back at the specified time if the customer answers the telephone but asks to respond to the survey at a different time; and

4)         call back at a time the target respondent is expected at home or office if the telephone is answered by anyone but the target respondent.

(Source:  Added at 24 Ill. Reg. 12914, effective September 1, 2000)