HOW DO I CHOOSE WHAT FORMULA IS NEEDED? ALSO, COULD YOU EXPLAIN HOW TO GET ANSWER. THANKS

A random sample of 81 UT business students revealed that on average they spent 6 hours per week on Facebook. The population standard deviation is assumed to be 1.8 hours per week.

1. Refer to Exhibit 8-1. If we want to develop a 95% confidence interval for the average time spent per week on Facebook by all UT business students, the margin of error of this interval is

a.0.392

b.1.960

c.0.208

d.1.645

1. Refer to Exhibit 8-1. The 95% confidence interval for the average time spent per week on Facebook by all UT business students is
2. 4.041 to 11.962 hours
3. 3.367 to 7.643 hours
4. 4.803 to 7.203 hours
5. 5.608 to 6.392 hours

Exhibit 8-2

A sample of 75 information system managers had an average hourly income of $40.75 and a standard deviation of $7.00.

18.Refer to Exhibit 8-2. When the 95% confidence interval has to be developed for the average hourly income of all system managers, its margin of error is

a.40.75

b.1.96

c.0.81

d.1.61

1. Refer to Exhibit 8-2. The 95% confidence interval for the average hourly income of all information system managers is
2. 40.75 to 42.36
3. 39.14 to 40.75
4. 39.14 to 42.36
5. 30 to 50