Fitting probability models to frequency data - X2 goodness of fit test

9 important questions on Fitting probability models to frequency data - X2 goodness of fit test

What discrepancy is measured with the X2 - goodness-of-fit test?

The discrpeancy between an observed frequency distribution and the frequencies exprected under H0.

What is the test statistic of the X2 goodness-of-fit test? What does this mean to the H0?

X2 -statistic. IT measures the discrepancy between observed and expected frequencies When X2 is too large the H0 is rejected.

What should the H0 entail within the proportional model?

The frequency of an event is proportional to the number of opportunities. F.e.; the frequency of births on mondays is the same proportion on every other day of the week.
  • Higher grades + faster learning
  • Never study anything twice
  • 100% sure, 100% understanding
Discover Study Smart

Why is it important to use absolute frequencies (counts) and not relative frequencies when calculating X2?

The wrong answer will be given, the X2 does calculate proportion/relative frequencies.

What does the number of degrees of freedom specify in accordance to the null distribution?

Df specified which of a familiy of distributions to use as the null distribution.

How is the degrees of freedom for a X2 goodness-of-fit test calculated? Give the formila

Df = (number of categories) - 1 - (number of parameters estimated from the data.

What would the X2 be if the data exactly matched the expectation of the null hypothesis, why?

0, because there is no discrepancy between the observed and expected frequency.

What is calculated when calculated a P-value for a X2 goodness of fit test?

The probability of getting a X2 value greater than a single specified value.

What does a critical value mark of a X2 probability distribution?

The critical value  is he value of a test statistic that marks a area in the tail of the sampling distribution under H0.

The question on the page originate from the summary of the following study material:

  • A unique study and practice tool
  • Never study anything twice again
  • Get the grades you hope for
  • 100% sure, 100% understanding
Remember faster, study better. Scientifically proven.
Trustpilot Logo