Final answer:
The 80th percentile of the given data is 28.35.
Step-by-step explanation:
To calculate the 80th percentile of the given data, first arrange the data in ascending order: 1.1, 7.9, 9.7, 19.3, 21.9, 26.1, 27.9, 28.8, 29.1, 29.4. Since the 80th percentile falls between the 40th and 41st values (27.9 and 28.8), we take the mean of these two values: (27.9 + 28.8) / 2 = 28.35.