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Exercise: Confidence intervals for mean FEV1

SPSS is extrraordinarily poor at calculating confidence intervls for simple statistics,
though it does them for many slightly more complicated ones.
It will not calculate the confidence interval for the difference between or the ratio of
two proportions, for example.
However, it will calculate the confidence interval for a mean and we shall use it to calculate some
confidence intervals for mean FEV1 in young men.

The file fev.sav contains the 57 FEV1 measurements used in the lecture.
Download the file and read it into SPSS.

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Questions

1. Using SPSS, calculate a 95% confidence interval for mean FEV1.
Give the confidence interval to two decimal places.

Check suggested answer 1.

2. Calculate a 99% confidence interval for mean FEV1.

Check suggested answer 2.

3. Calculate a 90% confidence interval for mean FEV1.

Check suggested answer 3.

4. How do the three confidence intervals differ?

Check suggested answer 4.

5. How would you write the standard error of the mean FEV1 to three decimal places?

Check suggested answer 5.

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Last updated: 3 November, 2006.

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