18- For an xbar and R control chart use the following summary statistics: x with equals on top = 10.0, top enclose r =2.3, and n=4 to answer the following questions. (Note: Use the above scenario and data to answer questions 18-20.) Calculate an unbiased estimate of sigma . a- 2.4965 b- 1.117 c- 2.039 d- 2.883 19- (Use scenario from question 18 above.) Calculate the upper control limit for an xbar control chart. a- 16.9 b- 13.35 c- 14.234 d- 11.677 20- (Use scenario from question 18 above.) Calculate the upper control limit for an R control chart. a- 5.249 b- 9.146 c- 14.234 d- 9.26 20- For an xbar and s control charts given the following summary statistics:x with equals on top =10.0, top enclose s =2.3, and n = 4. Calculate an unbiased estimate of sigma . a- 2.039 b- 1.117 c- 2.497 d- 2.883 22- Assume sigma gage = 2.497. The upper specification limit USL=16 and lower specification limit LSL=4. Using k=6, what is the precision-to-tolerance (P/T) ratio? a- 1.0195 b- 0.585 c- 1.2485 d- 1.4415 23- Twenty-five samples, of size 30 were collected and a total of 48 nonconforming items were found. The three sigma upper control limit for a p-chart is. a- 0.198 b- 0.091 c- 0.211 d- 0.833 24- Given that sigma process=4.7 and sigma gage=3.4. What is the total standard deviation in data from this process? a- 3.245 b- 8.1 c- 5.801 d- 33.65 25- Given an 3-sigma xbar chart for n=4 with UCL=16 and LCL=4, the estimated process standard deviation is. a- 4 b- 2 c- 16 d- 8