Final answer:
Using landlines exclusively to sample people for estimating the average age in Springfield is unreliable due to biases towards older residents and those often at home. A more representative method would involve using multiple communication channels and demographic weighting.
Step-by-step explanation:
Using a list of all landline telephones to contact a simple random sample of 300 people is not a reliable method to estimate the average age of all people in Springfield. Due to current trends in phone usage, many individuals favor cell phones over landlines. The Centers for Disease Control and Prevention (CDC) data reveals high percentages of certain age groups primarily use cell phones. Specifically, 83 percent of Americans aged 30-34, 74.5 percent of those aged 35-44, and nearly 60 percent of 45-64 year-olds. Consequently, the population sample would likely be biased towards older residents and those more frequently at home, therefore not representative of the city's entire population.
To correct for this, one approach may involve using multiple channels of communication to reach a more demographically varied and representative sample. This could include landline and cell phone contact, online surveys, and possibly face-to-face interviews in various city locations. In addition, demographic weighting might be necessary post-sampling to adjust for any potential biases and better reflect the city's population.