Which of the following statements is true about one-tailed tests of significance?

Which of the following statements is true about one-tailed tests of significance?
 
  a. The critical region is at both ends of the theoretical sampling distribution.
  b. They increase the chances of reaching the critical region if the results are in the predicted direction
  c. They are used mainly with very large samples.
  d. They require greater between-group differences in order to reach the critical region.

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The number of degrees of freedom in a cross tabulation table is one less than the number of rows times one less than the number of columns.
 
  Indicate whether the statement is true or false

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When we are testing directional hypotheses, we should:
 
  a. Never use a two-tailed test.
  b. Always use a two-tailed test.
  c. Use a two-tailed test if we want to be able to reject the null hypothesis in case our findings are in the opposite direction from the one predicted in our hypothesis.
  d. None of these.