The Communication and Publicity Committee in a certain school took a sample of 10 letters of communication. The grammatical lapses in each letter were counted and recorded as shown below. 16, 11, 9,...

The Communication and Publicity Committee in a certain school took a sample of 10 letters of communication. The grammatical lapses in each letter were counted and recorded as shown below. 16, 11, 9, 12, 15, 7, 2, 6, 6, 10 a.) Calculate the sample mean b.) Compute for the sample standard deviation c.) Construct a 90% confidence interval for the population mean of grammatical errors in the communication letters circulated in the institution