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Industrial Statistics with Minitab by Xavier Tort-Martorell Llabres, Lluis Marco Almagro, Pere Grima Cintas

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9.2 Hypothesis Testing and Confidence Interval for a Proportion

Stat > Basic Statistics > 1 Proportion

Example 9.2:
A certain consumer electronics product offers a new feature that increases its price. Nonetheless, it seems that only very few people use that feature. To confirm that, a survey is carried out among 200 users and it is found that only 17 clients use that feature. We are interested in:
1. Calculating a 95% confidence interval for the proportion of users that use the feature in question.
2. Do the data confirm the suspicion that less than 10% of users are making use of the new feature?

In this case, you do not need to enter the data in the worksheet. Instead, go directly to

Stat > Basic Statistics > 1 Proportion:

ch09fig009.eps

The result is:

ch09fig009.eps

Notice that the problem formulation guides us to choose the option ‘less than’ as alternative hypothesis, obtaining:

ch09fig009.eps

Given the obtained p-value of 0.285, clearly larger than 0.05, the survey data do not allow us to state that the percentage of users that use the new feature in question is less than 10%.

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