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Answers to the checkpoints of chapter 6

Checkpoint 1 

  • If there are differences between the sample and test value, and if the sample has a normal distribution.
  • The hypothesis is that the age is lower, so the hypothesis has a direction.
  • The null hypothesis is not rejected (p value = 0.0668; conclusion p > 0.005).


Checkpoint 2 

  • You would use a t test if the population variance is not known and (in some cases) for small samples.
  • From 120 onwards, the shape of the t distribution is the same as a normal distribution.
  • A critical value is the t value or the z value associated with the chosen significance level.


Checkpoint 3

  • If you have two dependent groups and the population variance is unknown.
  • Because there is an association in the data that has been collected.
  • No.


Checkpoint 4

  • In terms of whether the population variance is known or not known.
  • From n = 120 onwards.
  • That is a test in which the groups being compared have the same variance.
  • At df = 199, the critical t value is 1.96; if you perform a z test, the critical value is also 1.96, because the sample for this is sufficiently large.


Checkpoint 5

  • No, you don’t reject it; p = 0.06.
  • Yes, at 5% with a one-tailed test, you would.


Checkpoint 6

  • You could adjust the degrees of freedom.
  • You have made a Type I error.
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