Final answer:
To perform the hypothesis test, use the z-distribution and calculate the p-value to determine the probability of obtaining a sample mean as extreme or more extreme than the observed value, assuming the null hypothesis is true.
Step-by-step explanation:
To perform the hypothesis test in this scenario, you would use the z-distribution. Since the underlying population is assumed to be normal and the sample size is large enough, the z-distribution is appropriate. To calculate the p-value, you would compare the sample mean (12.8) to the population mean (13) using the formula z = (sample mean - population mean) / (sample standard deviation / sqrt(sample size)). Once you have the z-score, you can find the corresponding p-value using a standard normal distribution table or a calculator. The p-value indicates the probability of obtaining a sample mean as extreme or more extreme than the observed value, assuming the null hypothesis is true.