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Thread: Time 2 Sample Size

  1. #1
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    Time 2 Sample Size

    I was hoping for some advice. I'm looking at the same sample at 2 timepoints.
    At the first time point I had 95 participants and at follow up I only got 18 replies back.

    Is it worth doing any analysis between the two timepoints, or is the sample at time 2, too small for any reliable results.
    Having a quick look at the data, there is a significant positive correlation between Time 1 anxiety, depression with time 2.

    Many advice would be great

  2. #2
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    rogojel's Avatar
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    Re: Time 2 Sample Size

    I think that the problem is not so much the sample size but the fact that you might have a biased second sample.It is quite possible that there is some pattern in the respondents to the aecond query - i.e, if mostly those answered who had depression while those who did not just ignored the questions, it will look as if therebwas a realtionship even though there wouldn't be any in the whole population.


  3. #3
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    hlsmith's Avatar
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    Re: Time 2 Sample Size

    Yeah, this is a common issue. Most likely you are out of luck. Perhaps there is a pattern in characteristics of those who responded to both. If so, you may be able to solely generalize and interpret results solely to those patients.

    Ideally lost to follow-up is random, but typically empirically it is not.
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