Final answer:
Based on the provided sample data, the exact value of the population mean for yearly milk consumption cannot be determined; it remains unknown without further statistical testing or confidence interval construction. The correct answer is option a. 26
Step-by-step explanation:
The value of the population mean is one of the fundamental questions one might ask in statistics. However, when dealing with samples and trying to infer population parameters, we cannot simply assume that the sample mean is the population mean, especially without additional information or without constructing a confidence interval.
When a sample of 26 people reveals a mean yearly milk consumption of 84 gallons with a standard deviation of 26 gallons, this does not provide the exact value of the population mean but rather an estimate of it from the sample data. To determine the population mean with a degree of certainty, a hypothesis test or confidence interval would need to be constructed. Without doing so, the best answer we can give with the information provided is that the population mean is unknown.