Inferential Statistics
(c) Carry out a test of significance to decide whether Cal Poly students tend to carry less than 10% of their body weight.
1. Define the parameter(s) of interest. [Hint: Is the response variable quantitative or categorical?]
2. State the hypotheses both in symbols and in words.
3. Identify an appropriate test procedure and state and if a theorybased test comment on the validity conditions.
4. Use technology to determine a test statistic and pvalue for these hypotheses.Also report a 95% confidence for the parameter of interest.
Press one of the links below to view the appropriate technology instructions.
 From your previous results, use the ratio hot spot to select Test Mean
 Specify the hypothesized value of the population mean.
 Press OK
 For the confidence interval: Retrace your steps and select Confidence Interval > 0.95.


 Choose Stat > Basic Statistics > One Sample t
 Double click on the ratio variable so it appears in the One or more samples box.
 Check the box to Perform hypothesis test and specify the hypothesized value of the population mean.
 Press the Options button and choose the form of the alternative hypothesis.
 Press OK
 For the confidence interval: Retrace your steps and use a twosided alternative.


 t.test(backpackdata$ratio, mu=XX, alternative="XXX")
 Enter the hypothesis population mean for XX.
 Enter less, greater, or two.sided for XXX.
 For the confidence interval: Retrace your steps use "two.sided" for the alternative.

 Open the Theory Based Inference applet.
 Use the pulldown menu to select the One mean scenario.
 Check the Paste data and Includes header boxes.
 Paste in the ratio data from the Excel file.
 Press Use Data. (You should be able to verify the sample size, mean, and standard deviation values.
 Check the Test of significance box. Specify the hypothesized value for the population mean and toggle the alternative direction. Press Calculate
 For the confidence interval: check the Confidence interval box.


Copy the relevant output into your report.
5. State your decision and summarize your conclusions in context. Be sure to reference information from the output! (Meaning, cite the test statistic, pvalue, and confidence interval!)