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    HI all,

    I am struggling a little to understand fully hypothesis testing with the product and moment correlation. I have no problem calculating the coefficients, and I know if the coefficient is higher than the critical value then you reject the null hypothesis and conversely you fail to reject the null hypothesis if the coefficient is less than the critical value.

    I am confused with choosing between 1 and 2 tailed tests. I know if the question says 'test that the mean isn't 'X'' it is 2 tailed, and 'test that the mean is greater than or less than' it is 1 tailed. However, the wording on my assignment with regards to the hypothesis testing with the product moment and spearman's rank correlation is confusing.

    for product moment correlation:

    Test at 1% significance whether there is a negative correlation between % moisture content and and calorific value.

    For spearman rank correlation:

    Calculate spearman's rank coefficient bewteen x and y and test at the 10% level of significance

    How do I know how to do 1 or 2 tailed tests for these?

    Thanks in advance!
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    I believe because it specifies 'negative correlation' that means it is a one-tailed test because you are only looking at one side of the results.

    Whenever is is a general question like the second one, assume it is a two-tailed test.
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    Thankyou!
 
 
 
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Updated: January 30, 2017
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