How We Gather (and How to Interpret) Our Data
Last updated October 2023
Our tables rating individual companies will be more valuable to you if you know how the data were gathered and how they should be interpreted.
Opinion Surveys
We regularly survey area consumers for their feedback on services they have used. We primarily survey our subscribers, but also invite other randomly selected consumers to provide ratings.
On our surveys, we ask consumers to rate their experiences with services they had most recently used on several aspects of service. Our ratings tables show the percent of each company’s surveyed customers who provided a rating of “superior” (as opposed to “inferior” or “adequate”) for questions on our survey.
Our ratings tables include all of the service providers for which we received at least 10 ratings on our customer surveys. If a company is not listed on our ratings tables, it simply means we did not receive at least 10 ratings for it.
Since many companies were rated by rather small numbers of raters, small differences between two firms in the percentage of raters who gave a particular rating (say, “superior”) should be ignored. The table below gives a rough guide to minimum differences you should look for in deciding on one company over another.
When using these survey data, remember that the questions are to some degree subjective and that the differences among companies might be explained by differences in the personalities, backgrounds, critical standards, and other characteristics of the raters or by biases these raters might have.
Complaints
For many of the services we evaluate, our ratings tables show the number of complaints filed against each company with government offices of consumer affairs in Fairfax, Howard, and Montgomery counties; the Consumer Protection Division of the Maryland Attorney General’s Office; and the Virginia Office of Consumer Affairs. These complaint counts are for a two-year period. Our ratings tables also often show counts of complaints filed with the Better Business Bureau for a three-year period.
Where we were able to, we have also reported on our ratings tables a complaint rate for each company, calculated by dividing the number of complaints by our measure of the number of full-time-equivalent employees who perform non-commercial work for the company. These complaint rates are intended as a rough way to take into account volume of work and the fact that companies that do more work are exposed to a greater risk of incurring complaints.
When using the complaint information, keep in mind that complaints are not always justified; sometimes the customer is unreasonable. Also, be aware that some companies may be at greater risk than others of incurring complaints because of the specific types of business they do. And remember that the measure of business volume we use in calculating complaint rates (our estimate of the number of full-time-equivalent employees who perform non-commercial work) is at best a very rough indicator.
We always recommend that you look for substantial differences in complaint counts and rates. We also advise giving little weight to complaint counts if the total count against a company is less than three or four.
Timeliness of the Data
All of the data must be interpreted in view of timeliness.
Our customer survey data are from surveys conducted from January 2012 to November 2024. Survey respondents were asked to report on experiences in the preceding year. Our data on complaints for the Better Business Bureau are for a three-year period dating back from a date in September 2023. Our data on complaints for the government offices of consumer affairs are for a two-year period between June 1, 2021 and May 31, 2023. Our price data were collected from June to September 2023. The data from our surveys of companies to ask about facts such as areas served were collected from July to September 2023.
For the most part, our tables include companies for which we collected 10 or more ratings on our customer survey during the customer survey period mentioned above, but we do not report data for periods prior to companies’ changes of name and ownership. As a result, some large companies are not listed at all. If only name or ownership changed, we do report the data. Changes subsequent to the dates listed above may not be taken into account.
Top Ratings
We give checkmarks to companies that score highest on a scoring system that we devise for each service field. Our scoring systems weight the various data in our tables and text based on our subjective judgment of their importance. Since the scores are based entirely on information presented, you can apply your own subjective judgments, and decide whether you prefer companies we have not given checkmarks. Where we do not have important data on a company, we cannot give our checkmark.
| A Rough Guide for Deciding Whether the Difference Between Two Percentages is Important | If one company had this number of ratings: | And a second company had this number of ratings: | Do not give much importance to the difference between the frequency with which the two companies experience a particular rating or result unless the difference is at least this many percentage points: |
|---|---|---|---|
| Assuming the average of the two companies' percentages is 50 percent | 10 30 60 120 |
10 30 60 120 |
45 26 18 13 |
| Assuming the average of the two companies' percentages is 80 percent | 10 30 60 120 |
10 30 60 120 |
36 21 15 10 |