A few days ago

PLEASE HELP !! Are there any genius statisticians out there???

if a two-sided null hypothesis is rejected for a single mean at a given significance level, the corresponding one- sided null hypothesis (i.e., the same sample size, the same standard deviation, and the same mean) will_________ be rejected at the same significance level.

a. Always b. Sometimes c. Never

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A few days ago

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b. Sometimes

Say you’re looking for 95% confidence. Your threshold for rejecting the null on each side of the curve for the z value will be at +/- 1.96. For a one-sided test the threshold will be either +1.65 or -1.65. If you have a calculated z value of -2.0 the null will definitely be rejected for 2-sided, but either accepted or rejected for one-sided depending on whether your threshold is +1.65 or -1.65. That depends on whether you are looking for your mean to be greater or less than your null.