A common rule of thumb is that for a sample containing more than 50 observations, we use the z-table instead of the t-table. However, let's suppose that we have a sample of more than 50 observations, and the population variance is unknown. Should we use the t-statistic in this case? Thanks

Hi Mohamed, As you have learned the z-distribution assumes that the population standard deviation is known. On the other hand, the t-distribution is based on the sample standard deviation. When you have more than 50 observations you can use the z-distribution because the sample starts to approximate the population distribution close enough. Hope this helps! Best, Ned

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Mohamed El Hamly

Last answered:

05 Jan 2023

Posted on:

03 Jan 2023

T-statistic vs Z-statistic

in Statistics / Population variance unknown, t-score

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Ned Krastev

Instructor

Posted on:

05 Jan 2023

T-statistic vs Z-statistic

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