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- Topic: Confidence Intervals - Which Test?

Author | Topic: Confidence Intervals - Which Test? |
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GeorgeC@2009-12-19 09:41:35 |
Could someone just confirm whether or not the z score is ok to use when sample size is >=30 when the population distribution is not normal and the variance is unknown? I know t can be used but is z just as acceptable or should it always be t? Thanks |

gelar005@2010-01-19 14:44:33 |
If the population is normally distributed, and the population variance is known, use a z-score irrespective of sample size. If the population is normally distributed, and the population variance is unknown, use a t-score irrespective of sample size. If the population is not normally distributed, and the population variance is known, use a z-score only if n >= 30, otherwise it cannot be done. If the population is not normally distributed, and the population variance is unknown, use a t-score only if n >= 30, otherwise it cannot be done. |