The chancellor at City University is worried that the grades have fallen in the past year. The grade point average for graduating students in the previous 5 years was 2.80 with a standard deviation of 0.25. The chancellor randomly samples 10 seniors from this year's graduating class and obtains the following GPAs: 2.40, 2.80, 2.65, 2.15, 2.65, 2.72, 2.42, 2.70, 2.52, 2.49. What can the chancellor conclude? Use a two-tailed test at the.05 significance level
H0: Null Hypothesis: = 2.80
HA: Alternative Hypothesis: 2.80
From the given data, the following statistics are calculated:
n = 10
= 2.55
s = 0.1937
SE = s/
= 0.1937/
= 0..0613
Test statistic is given by:
t = (2.55 - 2.80)/0.0613
= - 4.0783
= 0.05
ndf = n - 1 = 10 - 1 = 9
From Table, critical values of t = 2.2622
Since the calculated value of t = - 4.0783 is less than critical value of t = - 2.2622, the difference is significant. Reject null hypothesis.
Conclusion:
The data support the Chancellor's worry that the grades have fallen
in th past year.
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