The test statistics based on the information given will be 0.238.
Population mean = 28.3
Sample mean = 28.2
Standard deviation = 4
Sample size = 90
In this case, the z test will be used since the standard deviation is known. This will be:
= (28.2 - 28.3)/4/✓90
= -0.1/(4/9.48)
= -0.1/0.42
= -0.238
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