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Thread: Confidence interval question

  1. #1
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    Confidence interval question

    Fr a sample of 100 hypertensive patients, we find that a 95% confidence interval of systolic BP to be [130, 150]. What statement is FALSE?

    A- if a drug is given that makes the patients BP more variable, then the resulting CI of the post-treatment BP will be wider.

    B-A 90% CI of the BP based on the same data will be narrower.

    C-If a drug is given to exactly reduce the BP by 10 units in every patient, then the CI post Treatment will be narrower.

    D-A 95% CI on a random subset of 60 patients is going to be wider.

    I'm having trouble wrapping my head around this problem. I thought the answer was C, but now I'm questioning myself. Any thoughtS??

  2. #2
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    Karabiner's Avatar
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    Re: Confidence interval question

    C tells you that the CI will be narrower if the mean blood pressure decreases by 10. You should perhaps check the formulas for the calculation of standard errors and CIs - is it the sample mean on which the width of the CI depends, or is it sample variance, or maybe both?

    With kind regards


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