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 0.19 words per minute. A previous study found that the mean was 28.3 words per minute. Assuming that the variance is 29.16, what is the minimum number of third graders that must be included in a sample to construct the 98% confidence interval? Round your answer up to the next integer.

Answer 1

for 98 % CI value of z=	2.33
standard deviation σ=	5.40
margin of error E =	0.19
required sample size n=(zσ/E)2                                         =	4386.0

(try 4371 or 4372 if z values are taken  from calculator and not from table and revert)