Answer:
The 68% confidence interval for the population proportion of college seniors who plan to attend graduate school is (0.16, 0.24).
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of
, and a confidence level of
, we have the following confidence interval of proportions.

In which
z is the zscore that has a pvalue of
.
A recent survey showed that among 100 randomly selected college seniors, 20 plan to attend graduate school and 80 do not.
This means that 
68% confidence level
So
, z is the value of Z that has a pvalue of
, so
.
The lower limit of this interval is:

The upper limit of this interval is:

The 68% confidence interval for the population proportion of college seniors who plan to attend graduate school is (0.16, 0.24).