"\\bar x=28, \\;\\;s=3.71."
One sample t-test should be used.
Null hypothesis "H_0:\\;\\mu=30."
Alternative hypothesis "H_a:\\;\\mu<30."
Test statistic: "t=\\frac{\\bar x-\\mu}{\\frac{s}{\\sqrt{n}}}=-1.70."
Degrees of freedom: "df=10-1=9."
P-value (from t-table): "p=0.061."
Since P-value is greater than 0.05, fail to reject the null hypothesis.
She did not keep her promise.
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