Please help solve

Question

You want to obtain a sample to estimate a population proportion. Based on previous evidence, you believe the population proportion is approximately 72%. You would like to be 90% confident that your estimate is within 3.5% of the true population proportion. How large of a sample size is required

Answer 1

We know that the margin of error equation is E=z×p×(1-p)÷√n

Start with solving for the sample size in the same way Algebra taught you how to "solve for x", since that is the thing the problem is asking for. We know that we want a maximum tolerance of 3.5%, so E=0.035. We also know that past experience tells us that the proportion is 72%, so p=0.72. We also want to be 90% confident in our solution, so find the two-tailed critical value for 90%.

Plug those numbers into your calculator and round the answer up to the next integer. The reason for that specific wording is that both 191.1 and 191.9 would "round up to the next integer" to come out with 192