Answer:
Step-by-step explanation:
1) The confidence interval is calculated as the following
Hence, the confidence interval is
11) Under two sid t-tailed test, the null hypothesis
Against the alternative hypothesis
Under null hypothesis
The degree of freedom is n - 1 = 140
From the t - table at 5% level of significance under two - tail is 1.96
Since , calculated value is lowe than the tabulated value, we do not reject the null hypothesis.