After taking a speed-reading course, students are supposed to be able to read faster than they could before taking the course. A pilot sample of n = 25 students showed a mean increase of 300 words per minute with a standard deviation equal to 60 words per minute. To estimate the population mean with 95 percent confidence and a margin of error of ±10 minutes, the required sample size is approximately 139 students.

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Quizplus · Accepted Answer

The sample size is calculated using the formula n = (Z^2 * s^2) / E^2, where Z is the z-score for the desired confidence level, s is the sample standard deviation, and E is the margin of error. Plugging in the given values, we get n = (1.96^2 * 60^2) / 10^2 = 138.24. Rounding up to the nearest whole number, the required sample size is approximately 139 students.

After Taking a Speed-Reading Course, Students Are Supposed to Be