First, it is Consumer Reports (CR), not CU (Consumer ????).
Secondly, if the poll is biased toward people who had problems with the drive unit, the size of the sample is irrelevant to the statistical validity of the poll results.
The data for CR is collected and presented by the team of professionals, including automotive engineers and statisticians. Based on proper statistical analysis they decide if the sample is large enough for the data to be valid. If the sample is not big enough to draw conclusions they, instead of presenting data, mark the cell with an asterisk indicating "insufficient data". See couple of snapshots with the reliability data for MB Class S - CR did not include any data for the 2011 column because of the "insufficient data".
BTW according to this statistical data the MB flagship has reliability that is -126% worse than a group of peers, with CR reports categorizing it as "much worth than average". MS is categorized as "Average" and has reliability 6% worth than New hybrids/EVs.
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