Which statement correctly contrasts a population parameter with a statistic?

• A. Parameter is an observed statistic from the sample.
• B. Parameter is a fixed population value; statistic is independent of the sample.
• C. Statistic is fixed, while the parameter is random.
• D. Parameter is fixed; while a statistic is computed from a sample and estimates the parameter.

Answer: (D)

The main idea is that a population parameter is a fixed value that describes the entire population, while a statistic is a number computed from a sample and serves as an estimate of that fixed parameter. Because the sample can vary, the statistic can take on different values from one sample to another, making it a random variable. The parameter, in contrast, does not change with the sample—it’s fixed (though often unknown). So the statement that best fits is that a parameter is fixed, while a statistic is computed from a sample and estimates the parameter. The other descriptions mix up these roles: one treats the parameter as something observed directly in the sample, another says the statistic is independent of the sample, and another suggests the statistic is fixed while the parameter is random, which goes against the standard view.