First, let us break down 28 hours 36 minutes into minutes.
Number of minutes taken to grade 220 essays = (28 x 60) + 36 = 1680 + 36 = 1716 minutes
Now, we can find the average time taken to grade an essay by dividing the time taken to grade 220 essays by 220.
Average amount of time taken to grade an essay = = 7.8 minutes, or 7 minutes and 48 seconds
Answer:
The 95% confidence interval for the proportion of students who get coaching on the SAT is (0.1232, 0.147).
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 z-score that has a p-value of .
427 had paid for coaching courses and the remaining 2733 had not.
This means that
95% confidence level
So , z is the value of Z that has a p-value of
, so
.
The lower limit of this interval is:
The upper limit of this interval is:
The 95% confidence interval for the proportion of students who get coaching on the SAT is (0.1232, 0.147).