The average length of time for students to register for fall classes at a certain college
has been 50 minutes with a standard deviation of 10 minutes. A new registration
procedure using modern computing machines is being tried. If a random sample of
12 students had an average registration time of 42 minutes with a standard
deviation of 11.9 minutes under the new system, test the hypothesis that the
population mean is now less than 50, using a level of significance of (a) 0.05, and (b)
0.01. Assume the population of time to be normal.
The following null and alternative hypotheses need to be tested:
"H_0:\\mu\\geq50"
"H_1:\\mu<50"
This corresponds to a left-tailed test, for which a t-test for one mean, with unknown population standard deviation, using the sample standard deviation, will be used.
Based on the information provided, the significance level is "\\alpha=0.05," and the critical value for a left-tailed test for "\\alpha=0.05" and "df=n-1=12-1=11" degrees of freedom is "t_c=-1.795885." The rejection region for this left-tailed test is "R=\\{t: t<-1.795885\\}."
The t-statistic is computed as follows:
Since it is observed that "t=-2.328808<-1.795885=t_c," it is then concluded that the null hypothesis is rejected. Therefore, there is enough evidence to claim that the population mean "\\mu" is less than 50, at the "\\alpha=0.05" significance level.
Using the P-value approach: The p-value for left-tailed, "t=-2.328808, df=11," "\\alpha=0.05" is "p=0.01997," and since "p=0.01997<0.05," it is concluded that the null hypothesis is rejected.
Therefore, there is enough evidence to claim that the population mean "\\mu" is less than 50, at the "\\alpha=0.05" significance level.
Based on the information provided, the significance level is "\\alpha=0.01," and the critical value for a left-tailed test for "\\alpha=0.01" and "df=n-1=12-1=11" degrees of freedom is "t_c=-2.718078." The rejection region for this left-tailed test is "R=\\{t: t<-2.718078\\}."
The t-statistic is computed as follows:
Since it is observed that "t=-2.328808>-2.718078=t_c," it is then concluded that the null hypothesis is not rejected. Therefore, there is not enough evidence to claim that the population mean "\\mu" is less than 50, at the "\\alpha=0.01" significance level.
Using the P-value approach: The p-value for left-tailed, "t=-2.328808, df=11," "\\alpha=0.01" is "p=0.01997," and since "p=0.01997>0.01," it is concluded that the null hypothesis is not rejected.
Therefore, there is not enough evidence to claim that the population mean "\\mu" is less than 50, at the "\\alpha=0.01" significance level.
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