Question

Week 1	Week 2	Week 3	Week 4	Week 5
3.98	5.52	5.79	3.98	5.14
4.99	5.52	6.42	5.79	6.25
5.15	4.98	4.88	5.77	4.89
5.23	4.28	4.02	4.3	5.99
4.77	5.12	4.76	6.41	6.35
5.21	5.08	5.08	4.55	5.11
5.51	5.86	4.58	6.02	6.02
4.95	4.95	5.44	5.95	4.28

Create a new sheet in the same file, and use it to answer the following:

A variety of packaging solutions exist for products that must be kept within a specific a temperature range. Cold chain distribution is particularly useful in the food and pharmaceutical industries. A packaging company strives to maintain a constant temperature for its packages. It is believed that the temperature of its packages follows a normal distribution with a mean of 5 degrees Celsius and a standard deviation of 0.3 degree Celsius. Inspectors take weekly samples for 5 weeks of 8 randomly selected boxes and report the temperature in degrees Celsius in the attached file (link above).

a. Construct in Excel an xbar chart for quality control. Plot the five weekly sample means on the xbar chart.

b. Does it appear that the process is in control? Explain.

Hint: read page 235 on how to create a control chart.

Answer 1

Creating X -bar and chart in excel

Step - by step procedure

1. first bring data in to excel sheet.

2. find the control chart table of contents (Biasing Constraints) from internet. This will help to calculate Lower and upper control limit.

3. Our sample size is 8 . so A3 = 1.099, B3 = 0.185, B4 = 1.815

4. Now we need to calcluate X-bar,St.dev,UCL's,LCLx,X bar-bar, and UCLx

5.X-bar is an average of week (calculation in row wise) "formula = "=IF(C5="","",AVERAGE(C5:N5))"

6. st.dev = =IF(C5="","",STDEV(C5:N5))

7.S-bar = average(st.dev)

8. LCLs = B3* S-bar

9.UCLs = B4* St.dev

10. LCLx = (X bar-bar) - (A3 * S-bar)

11 X bar-bar = Average (S-bar)

12 UCLx = (X bar-bar) + (A3 * S-bar)

b. Does it appear that the process is in control? Explain

As per the chart process is in perfect control

both x-bar and x double are under the upper control.