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Page 4
Test Yourself
I. Confidence Interval (Proportion)
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Ages of Patients |
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21
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32
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26
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24
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30
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22
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25
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24
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31
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27
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32
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29
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20
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22
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26
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27
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28
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24
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30
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23
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1. Calculate the standard error using the 7 patients already selected. Use the proportion of sampled patients over the age of 25.
hint: p=?/7
2. Build a confidence interval.
3. Is the true value contained in the interval?
4. Is this confidence interval helpful?
II. Confidence Interval (Mean)
1. Using systematic sampling select 5 patients from this table.
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Ages of Patients |
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21
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32
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26
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24
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30
|
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22
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25
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24
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31
|
27
|
|
32
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29
|
20
|
22
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26
|
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27
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28
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24
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30
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23
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2. Calculate the sample mean.
3. Calculate the variance.
4. Calculate the standard error.
5. Calculate your confidence interval.
Is the true mean (26.2) within your interval? If not, remember that we set alpha or type I error at 5%. You could be the 5 out of 100 whose interval doesn't contain the true value, but I doubt it. Check your math and if you can't find a mistake, try using a different sample.