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# Hypothesis testing question (edexcel S2) Watch

1. I dont get what is going on here:

John wished to see if a coin was unbiased towards coming down heads. He decides that the level of significance of his test will be 5%.

If the random variable X represents the number of heads, what values of X would cause the null hypothesis to be rejected?

H0: p = 0.5 (the coin is not biased)

H1: p>0.5 (the coin is biased towards heads)

The probability of getting 7 or 8 heads is

3.1% + 0.4% = 3.5% (these values have been calculated using binomial
distribution X-B(8,0.5)

This is less than 5% and either X=7 or X=8 would cause the null hypothesis to be rejected.

Right, so this is my question:

Surely, if the probabiity of getting 7 or 8 heads is less than 5%, then it would lead to the null hypothesis NOT being rejected?

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Updated: December 29, 2010
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