Currently patrons at the library speak at an average of 60 decibels. Will this average change after the installation of a new computer plug in station? After the plug in station was built, the librarian randomly recorded 40 people speaking at the library. Their average decibel level was 58.6 and their standard deviation was 9. What can be concluded at the the = 0.01 level of significance?

1. For this study, we should use Select an answer t-test for a population mean z-test for a population proportion
2. The null and alternative hypotheses would be:

H0:H0: ? p Select an answer > = <

H1:H1: ? p Select an answer > = <

1. The test statistic ? t z = (please show your answer to 3 decimal places.)
2. The p-value = (Please show your answer to 4 decimal places.)
3. The p-value is ? >
4. Based on this, we should Select an answer reject accept fail to reject the null hypothesis.
5. Thus, the final conclusion is that ...

• The data suggest the population mean has not significantly changed from 60 at = 0.01, so there is statistically significant evidence to conclude that the population mean decibel level at the library has not changed since the plug in station was built.
• The data suggest the populaton mean has significantly changed from 60 at = 0.01, so there is statistically significant evidence to conclude that the population mean decibel level at the library has changed since the plug in station was built.
• The data suggest that the population mean decibal level has not significantly changed from 60 at = 0.01, so there is statistically insignificant evidence to conclude that the population mean decibel level at the library has changed since the plug in station was built.