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QNT 561 Statistical Quality Control
Questions on Regression and Statistical Quality Control
1) A researcher demonstrated a correlation of r = 0.60 between teacher attire and student academic performance across 150 grade schools in her state. She concluded that encouraging teachers to be properly attired will increase academic performance. Do you agree or disagree with her conclusion? Why?
2) Does correlation equal causation? Does the strength of correlation depend on the direction? What is the meaning of a zero correlation? Explain your answers.
3)What does a ‘statistically significant’ result mean? How do we know whether a relationship between two variables is caused by something other than mere random chance?
4)What does a small p-value, lower than the level of significance indicate? Explain using specific examples
5) Does the strength of correlation depend on the direction? What is the meaning of a zero correlation? Explain your answers.
6) What is the purpose of using regression analysis? How may it be used to formulate strategies?
7) A private mail delivery service has a policy of guaranteeing delivery by 11:00 A.M. on the morning after a package is picked up. Suppose that the management of the service wishes to check the delivery performance in a particular area over a 2-week time period based on a five-day workweek. The total number of packages delivered daily and the number of packages that were not delivered by 11:00 A.M are shown below:
Day
Packages Delivered
Packages not Arriving before 11:00 A.M.
1
136
4
2
153
6
3
127
2
4
157
7
5
144
5
6
122
5
7
154
6
8
132
3
9
160
8
10
142
7
Based on the above data, can we conclude that the postal delivery process is out of control? [hint: if possible, create control limits and a p-chart for the above data].
