How did you calculate 98% confident as 2.326?

Question

The original question is: How large of a sample size is required?

The question reads as follows:

You want to obtain a sample to estimate a population proportion. Based on previous evidence, you believe the population proportion is approximately p∗=27%. You would like to be 98% confident that your esimate is within 2% of the true population proportion. How large of a sample size is required?

n = 

Do not round mid-calculation. However, use a critical value accurate to three decimal places.

I understand everything except how to calculate the 98% confidence part of the question. I thought it was invNorm(.98) with a Ti-84, but that does not get me 2.326. (oddly enough, invNorm(.99) does get me 2.326)

Answer 1

A 98% confidence interval means you leave 1% remaining on both tails. You can think of it spanning the 1st percentile and the 99th percentile (99-1 = 98) - hence why invNorm(.99) does get you 2.326.