The iPhone 4 has been for more than a month now--providing analysts, consumer advocates, and individuals with a of whether iPhone issues at AT&T are a , or the Apple smartphone itself. However, it is important with any survey to look behind the curtain and exercise some cautious skepticism. In this case, I think I'll take my AT&T iPhone 4 dropped calls survey with a side of salt.

For starters, how did ChangeWave conduct the survey? To get some perspective on the data, we need to know how many users from AT&T, and how many users from Verizon were questioned. We need to know whether users were randomly selected or chosen. We need to know if the survey results are indicative of a cross-section of the nation, or if they're concentrated in specific regions--like San Francisco and New York where AT&T is known to have more issues than other regions.

If Verizon has only had the iPhone 4 for a month, how can you ask users about their experience over the last 90 days?The actual question asked of users was "Over the past 90 days, how often have you experienced a 'dropped call' on your iPhone 4?". Well, first of all, Verizon users have only had the iPhone 4 for about a month, so it isn't a valid question, and second of all, asking users to take a stab at how many dropped calls they've experienced over such a significant length of time is much more anecdotal than scientific.

I am not saying the survey is skewed or biased. I am saying that I have no way of determining if it is or isn't because I don't have enough information about how the survey was conducted. The ChangeWave research team has not responded to my email or voicemail requests for more details.

Meanwhile, AT&T responded to point out that it conducts exhaustive real-world driving tests to ensure call quality and integrity, and that its own research indicates significantly lower rates of dropped calls than the ChangeWave survey reports.