The Professor's Response
For Homework 7.4 For number 42 n=128 so n-1=127 that number isnt on the t-table so how would you solve it? Also for homework 7.4 if the sample size is 30 or greater do we use the z-table?
See the professor's answer below.
Hi Natalie,
In that section, you are trying to distinguish between when to use a z-critical value or a t-critical value. Remember, we are using the simplified rule that states if n > 30, we will find a z-critical value, otherwise we will find a t-critical value. For example, in the problem you asked about, since n = 128, we need a z-critical value, so you do not need to find degrees of freedom to find the 1.282.
Hope that answers your question,
Professor McGuckian