|
Our tables rating individual firms will be more valuable to you if you know how the data were gathered and how they should be interpreted.
Customer survey scores reported on our tables are from our surveys of Consumer Reports and CHECKBOOK subscribers, conducted via mail and the Internet.
Since many firms 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 firm over another.
When using these survey data, remember that the questions are to some degree subjective and that the differences among firms might be explained by differences in the personalities, backgrounds, critical standards, and other characteristics of the raters or by biases these raters might have.
To gather much of the other information on our tables, we surveyed the firms. In general, our researchers surveyed firms by phone (sometimes without revealing their affiliation with CHECKBOOK), but in some cases data were collected by mail or from firms' websites, or phone responses were confirmed by mail follow-up.
To compute our price index scores, we calculated an average price for each job or item for all the firms that quoted on that job or item. Next we compared each firm's price to the average. One firm might come in at 120 percent of the multifirm average for a particular job, and another firm might come in at 90 percent. We took each firm's percentage score on each job or item, standardized it, and assigned a weight to each job or item, based on our judgment. We then averaged the standardized, weighted percentage scores to find how the firm compared to other firms overall. Finally, we multiplied this overall percentage score by a flat dollar amount, say, $100.
The price index score, then, is intended to indicate the relative prices we found for the firms, adjusted to the base of this flat dollar amount. These index scores are imperfect for various reasons: for instance, the jobs or items checked may not be representative; the weighting of various jobs or items in the index may not accurately reflect typical expenditure patterns; and the number of jobs or items is small.
All of the data must be interpreted in view of timeliness. Our price data were collected from December 2004 to March 2005.
For the most part, our tables include firms 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 firms' changes of name and ownership. As a result, some large firms 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.
We give checkmarks to firms 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 firms we have not given checkmarks. Where we do not have important data on a firm, we cannot give our checkmark.
|
