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A researcher would like to determine which brand of light bulbs burns the longest.

A simple random sample of $30\text{ Brand A bulbs}$ and $30\text{ Brand B bulbs}$ are tested by screwing the bulbs into two different sockets at the same time and measuring the average number of hours before the bulbs burn out.

What is wrong with this experimental design?


The sample size for each bulb is too small since the population of bulbs is theoretically infinite.


A simple random sample of $30\text{ bulbs}$ from each brand is adequate for studying light bulbs so there is nothing wrong with this design.


The type of socket used to test the bulbs is a confounding variable.


This should be a blind study where the researcher does not know which brand of bulb is being tested.


A simple random sample of bulbs is not necessary because there is no reason to believe that a bulb from one brand is different from any other bulb within the same brand.

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