Question

You have been asked to continue your analysis of the yearly sales of the Nikon D5 camera body at the population of stores that sells this item throughout the United States. One of the factors that need to be studied is the variability in the sales of this item for this population of stores. To complete this task, you select a random sample of stores and record the sales at these stores. This data is shown in appendix one below. At both the 10% and the 5% levels of significance, does the standard deviation in the sales of the unit at the stores differ from 50 units? Create also 90% and 95% confidence intervals for the variance and standard deviation of the sales of this camera. Explain their meanings. Use these intervals to perform the hypothesis tests you performed earlier in the problem.

Appendix One:

158     192     201     154     155     188     132     200     194     183     188

190     166     160     176     122     180     167     129     138     178     199

187     229     167     164     189     165     188     200    

Answer 1

We find the sample variance of the sample using Excel function "VAR()"

We get :

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