Volatile compounds in human blood serum were measured by purge and trap gas chromatography/mass spectrometry. For quality control, serum was periodically spiked with a constant amount of 1,2-dichlorobenzene and the concentration (ng/g = ppb) was measured. Find the mean and standard deviation for the following spike data and prepare a control chart. State whether or not the observations (Obs.) meet each criterion for stability in a control chart.

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Obs. Obs. Obs. Obs. Obs. Day (ppb) Day (ppb) Day (ppb) Day (ppb) Day (ppb) 1.05 91 1.13 147 0.83 212 1.03 290 1.04 1 0.70 101 1.64 149 0.88 218 0.90 294 0.85 3 0.42 104 0.79 154 0.89 220 0.86 296 0.59 0.95 106 0.66 156 0.72 237 1.05 300 0.83 7 0.55 112 0.88 161 1.18 251 0.79 302 0.67 30 0.68 113 0.79 167 0.75 259 0.94 304 0.66 70 0.83 115 1.07 175 0.76 262 0.77 308 1.04 72 0.97 119 0.60 182 0.93 277 0.85 311 0.86 76 0.60 125 0.80 185 0.72 282 0.72 317 0.88 80 0.87 128 0.81 189 0.87 286 0.68 321 0.67 84 1.03 134 0.84 199 0.85 288 0.86 323 0.68