An internet service provider (ISP) has experienced rapid growth in the past five years. As part of its marketing strategy, the company promises fast connections and dependable service. To achieve its objectives, the company constantly evaluates the capacity of its servers. One component of its evaluating is an analysis of the average amount of time a customer is connected and actively using the Internet daily. A random sample of 12 customer records shows the following daily usage times, in minutes. Complete parts a through d below.

254	322	309	327	301	350
320	282	287	377	368	337

a. Using the sample data, compute the best point estimate of the population mean for daily usage times for the ISP's customers.

319.50 minute(s)

(Round to two decimal places as needed.)

b. The managers of the ISP's marketing department would like to develop a 90% confidence interval estimate for the population mean daily customer usage time. Because the population standard deviation of daily customer usage time is unknown and the sample size is small, what assumption must the marketing managers make concerning the population of daily customer usage times?

The population distribution is approximately normal.

c. Construct and interpret the 90% confidence interval estimate for the mean daily usage time for the ISP's customers.The 90% confidence interval estimate is

_ minute(s)_ minute(s).

(Round to two decimal places as needed. Use ascending order.)