The management of a café wants to be confident that their coffee temperature is consistent through various circumstances such as long pick-up time, added milk, etc. To do so, they decided to undertake a statistical process control initiative to determine the consistency of temperature of different types of coffee. Ten random latté samples were selected every hour during a seven-hour shift, and the temperature of each cup of coffee was recorded. The following data was collected; the temperature is measured in degrees Celsius.
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
116
103
116
106
124
98
125
114
101
119
109
104
93
124
109
117
117
117
106
96
116
124
125
122
124
125
93
103
124
108
120
119
114
98
117
116
106
114
104
116
93
101
109
103
109
104
109
98
120
124
104
119
114
108
98
104
111
120
108
112
111
100
119
119
103
109
122
103
100
114
a. Calculate the upper control limit (UCL) and the lower control limit (LCL) for the R-chart and the X-chart.
b. Draw the control chart.
c. Is the coffee temperature consistent? Explain.