Has the Process Mean Changed?

Here’s an exercise from Pyzdek Institute Green Belt training. At a pharmaceutical company they have developed an IV drip device that has an advertised drip rate of 5 drops per minute. A sample of 10 “drippers” is taken from the process and tested by counting the number of drips that occur during a 10 minute span. The average for each dripper is found by dividing the total drops by 10. The results are (average drops per minute):

4.9
5.1
4.6
5.0
5.1
4.7
4.3
4.7
4.6
5.0

Use the t test to conduct a test of hypothesis and answer this question at a 95% confidence level: “Is the process producing IV drip devices that average 5 drops per minute?” Also use confidence intervals to answer the same question.

This video shows a way to answer these questions using the QI Macros software.

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Author: Thomas Pyzdek

Consultant, author, owner of The Pyzdek Institute