10. Ms. Libby Abby, Chief Personnel Officer for Alaska Oil & Gas Corporation wants to estimate the true mean time ...

9. The registrar at the University of Hawaii studied the grade point averages (GPAs) of students  over many years.  She discovered that the distribution is approximately normal with a mean of1.89 and a standard deviation of0.25.  (4pts)

a.What% of the students  have a GPA of2.90 or more? 

b.What% of the students  have a GPA between 2.07 and 2.48? 

c.What% of the students  have GPA of 1.88 or less?

d.What percent of the students  have a GPA of 1.89 or less?

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10. Ms. Libby  Abby, Chief Personnel  Officer  for  Alaska  Oil & Gas Corporation wants  to estimate  the true  mean  time between occurrences  of personnel  accidents that  might  provide  the  potential  for  lawsuits.  A  random  sample  of forty-nine accidents is taken from the company's  records  and the time between each accident and one preceding is recorded. This information  revealed a sample mean of23 days and  a standard deviation  of 4 days.  Find  the  65%  confidence  interval  for  the population  mean  time  between  accidents.  Assume  the  population  standard deviation is known; use the "z" procedure.