The grade-point averages (GPA) of a random sample of 6 students who joined PVL in the first semester of AY 2001-2002 wer

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The grade-point averages (GPA) of a random sample of 6 students
who joined PVL in
the first semester of AY 2001-2002 were recorded:


Student : 1
2 3
4 5 6
GPA (2nd Sem, AY 2005-2006) 1.8
2.4 2.5 2.0
1.7 2.0
GPA (1st Sem, AY 2006-2007) 2.0
1.9 3.0 2.5
2.4 2.0
Construct and interpret a 90% confidence interval for the mean
difference in the GPA,
assuming the distribution of the GPAs to be approximately normally
distributed. Is there
an evidence of decrease in GPA?