A research assistant randomly selected 75 undergraduate students from the list of all students enrolled in the psychology-degree program at a large university. She asked each of the 75 students, “How many minutes per day do you typically spend reading?” The mean reading time in the sample was 89 minutes, and the margin of error for this estimate was 4.28 minutes. Another research assistant intends to replicate the survey and will attempt to get a smaller margin of error. Which of the following samples will most likely result in a smaller margin of error for the estimated mean time students in the psychology-degree program read per day?

  • A. 40 randomly selected undergraduate psychology-degree program students.
  • B. 40 randomly selected undergraduate students from all degree programs at the college.
  • C. 300 randomly selected undergraduate psychology-degree program students.
  • D. 300 randomly selected undergraduate students from all degree programs at the college.

Answer: C


Increasing the sample size while randomly selecting participants from the original population of interest will most likely result in a decrease in the margin of error.

Question Difficulty: EASY

Objective: Students must first read and understand statistics calculated from a survey that was conducted. Then, students must use apply their knowledge about the relationship between sample size and subject selection on margin of error.

  1. mean – trung bình (n): the value obtained by dividing the sum of several quantities by their number; an average.
  2. samples (in Maths) = statistic & not SAMPLING (STATISTIC).
  3. margin of error (NP): sai số.
  4. estimate – sự đánh giá (n): an approximate calculation or judgment of the value, number, quantity, or extent of something.
  5. replicate – tái tạo (v): make an exact copy of; reproduce.