Question

An educational psychologist wishes to know the mean number of words a third grader can read per minute. She wants to ensure that the estimate has an error of at most 0.230.23 words per minute. A previous study found that the mean was 29.829.8 words per minute. Assuming that the variance is 23.0423.04, what is the minimum number of third graders that must be included in a sample to construct the 95%95% confidence interval? Round your answer up to the next integer.

Answer 1

Let the random variable X is defined as

X: Number of words a third grader can read per minute.

mu : Average number of words a third grader read per minute

Given : E = Permissible error = 0.23 and variance = sigma² = 23.04

Alpha: level of significance = 0.05

n = Minimum number of third grader

Minimum sample size n for estimate mu with (1-alpha)*100% confidence coefficient is given by

Minimum number of third grader = 385.