Digital PSAT Math Practice Question 21: Answer and Explanation

Question: 21

A marine biologist has conducted research into the population of blue whales over the past few decades. The estimated global blue whale population is plotted against the given year in the graph below:

Another scientist is reviewing the results of the marine biologist's observations and assessing the impact of measurement error on such an ambitious project. The scientist is considering two possible sources of measurement error: (1) random error from any factor that would affect the scientist's measurements and (2) systematic error from a problem in the overall setup of the data-gathering project. Which of the following would be the best way that the marine biologist's measurement error could have been minimized?

• A. Collecting whale population data from as many possible points from an even distribution throughout all the world's oceans
• B. Comparing the blue whale data to data of other whales, such as the sperm whale, fin whale, and killer whale
• C. Gathering data from a consistent single point in the Atlantic Ocean, doing so at the same day/time each year
• D. Consistently taking a sample from a 100-square-mile range of the Pacific Ocean and electronically tagging each whale that is observed to ensure no whale is counted twice

Correct Answer: A

Explanation:

(A) The arrangement described in choice (A) would ensure the most random gathering of data from as large a sample as possible, thereby minimizing both random error and systematic error. The other options focus on irrelevant or extremely narrow samples. Choice (B) has a major systematic error since it does not focus on gathering blue whale data. Instead, this choice focuses on comparing data. Choice (C) minimizes random error for this particular data point due to its consistent measurement. However, this choice has the systematic issue of not gathering a wide enough sample of data. Although choice (D) is superior to choices (B) and (C), it falls short of choice (A). Choice (D) limits the sample to a relatively small part of one ocean instead of considering blue whales all over the world.