Step 1 :Given that the sample mean GPA of night students (\(\bar{X}_1\)) is 2.18, the standard deviation of the GPA of night students (\(s_1\)) is 0.9, and the number of night students sampled (\(n_1\)) is 25.
Step 2 :Also, the sample mean GPA of day students (\(\bar{X}_2\)) is 2.53, the standard deviation of the GPA of day students (\(s_2\)) is 0.85, and the number of day students sampled (\(n_2\)) is 35.
Step 3 :We are testing the claim that the mean GPA of night students is less than the mean GPA of day students, so we can set \(\mu_1 - \mu_2\) to 0 in the formula for the test statistic.
Step 4 :Substitute these values into the formula for the test statistic: \[Z = \frac{(\bar{X}_1 - \bar{X}_2) - (\mu_1 - \mu_2)}{\sqrt{\frac{s_1^2}{n_1} + \frac{s_2^2}{n_2}}}\]
Step 5 :Calculate the test statistic to get \(Z = -1.52\)
Step 6 :Final Answer: The test statistic, rounded to 2 decimal places, is \(\boxed{-1.52}\)