Workshop 2: Histograms and Descriptive Statistics

The tools practiced in this workshop are:

• Histograms
• Descriptive statistics

Situation:

Consider that you/your group works for a housekeeping company and you have been tasked with collecting data to document the current status of your cleaning performance. This data is needed to establish a baseline measurement at the beginning of your Lean Six Sigma project so that you will have a measurement to compare against later once the process has been improved.

Please note that the customer specifications for your cleaning service process are:

Target: 30 5 minutes (lower specification limit: 25 min and upper specification limit: 35 min).

Your baseline data of cleaning times is provided. Use Microsoft Excel to calculate your descriptive statistics and create a histogram of your data.

1. For the cleaning times documented by your cleaning process, what is the:
   1. Average cleaning time in minutes?
   2. Standard deviation in minutes?
   3. Range in minutes?
2. Create a histogram that summarizes your data set (i.e., measurements of the cleaning times in minutes) Your histogram should have at least 10 bars:
3. Near the end of your Lean Six Sigma project, after you have implemented solutions to improve your cleaning process, you measure the process performance again and get the following results:

Cleaning time Average: 30 minutes; standard deviation: 15 minutes cm; range: 10-75 min

1. Have you improved the process? Yes or no and why.

Hint: Perform a before and after comparison by comparing the baseline measurements in Activity #1a-c of this Workshop with the measurements given in this question.

2. How well does the improved process fulfill customer requirements?

Hint: Perform another comparison by comparing the measurements given in this question to the customer specifications given in the Situation part of this Workshop.

B C Job Cleanup 1 Number Time 2 Job 1 18 3 Job 2 20 4 Job 3 20 5 Job 4 20 6 Job 5 37 7 Job 6 55 8 Job 7 37 9 Job 8 20 10 Job 9 37 11 Job 10 29 12 Job 11 33 13 Job 12 33 14 Job 13 14 15 Job 14 100 16 Job 15 98 17 Job 16 20 18 Job 17 73 19 Job 18 14 20 Job 19 50 21 Job 20 25 22 Job 21 40 23 Job 22 120 24 Job 23 18 25 Job 24 44 26 Job 25 24 27 Job 26 10 28 Job 27 106 29 Job 28 22 30 Job 29 15 31 Job 30 40 32 Job 31 50 33 Job 32 30 34 Job 33 58 35 Job 34 43 36 Job 35 20 18 28 16 20 58 32 16 35 40 16 37 Job 36 38 Job 37 39 Job 38 40 Job 39 41 Job 40 42 Job 41 43 Job 42 44 Job 43 45 Job 44 46 Job 45 47 Job 46 48 Job 47 49 Job 48 50 Job 49 51 Job 50 52 Job 51 53 Job 52 54 Job 53 55 Job 54 56 Job 55 57 16 18 22 22 55 31 20 15 21 55