Biostatistics- Ch. 8 (Goodness of Fit
Tests) Quistions and Answers
Test statistic- ...ANSWER...a number calculated from the data and the null hypothesis
that can be compared to a standard distribution to find the P-value of a test
Discrete distribution- ...ANSWER...a probability distribution describing a discrete
numerical random variable
-ex. number of heads from 10 coin flips
X2 Goodness of Fit Test- ...ANSWER...compares count data to a model of expected
frequencies of a set of categories
Hypotheses for X2 Test: ...ANSWER...Ho: the data come from a particular discrete
probability distribution
Ha: the data do not come from a particular discrete probability distribution
The larger the X2 value is, the ______ the discrepancy there is between the data and
the frequencies expected under the null hypothesis ...ANSWER...greater
Degrees of freedom- ...ANSWER...specifies which X2 distribution to use as the null
distribution
How to calculate df: ...ANSWER...df= (number of categories) - 1 - (number of
parameters estimated from the data)
Critical value- ...ANSWER...-the value of a test statistic where P= alpha
-the value of a test statistic that marks the boundary of a specified area in the tail (or
tails) of the sampling distribution under Ho
Assumptions of X2 Test: ...ANSWER...-Random sample
-No more than 20% of categories have expected frequencies with < 5
-No category with expected frequency < or equal to 1
When can a X2 test be used as an approximation of a binomial test? ...ANSWER...If the
number of data points is large, then a X2 goodness-of-fit test can be used in place of a
binomial test
Tests) Quistions and Answers
Test statistic- ...ANSWER...a number calculated from the data and the null hypothesis
that can be compared to a standard distribution to find the P-value of a test
Discrete distribution- ...ANSWER...a probability distribution describing a discrete
numerical random variable
-ex. number of heads from 10 coin flips
X2 Goodness of Fit Test- ...ANSWER...compares count data to a model of expected
frequencies of a set of categories
Hypotheses for X2 Test: ...ANSWER...Ho: the data come from a particular discrete
probability distribution
Ha: the data do not come from a particular discrete probability distribution
The larger the X2 value is, the ______ the discrepancy there is between the data and
the frequencies expected under the null hypothesis ...ANSWER...greater
Degrees of freedom- ...ANSWER...specifies which X2 distribution to use as the null
distribution
How to calculate df: ...ANSWER...df= (number of categories) - 1 - (number of
parameters estimated from the data)
Critical value- ...ANSWER...-the value of a test statistic where P= alpha
-the value of a test statistic that marks the boundary of a specified area in the tail (or
tails) of the sampling distribution under Ho
Assumptions of X2 Test: ...ANSWER...-Random sample
-No more than 20% of categories have expected frequencies with < 5
-No category with expected frequency < or equal to 1
When can a X2 test be used as an approximation of a binomial test? ...ANSWER...If the
number of data points is large, then a X2 goodness-of-fit test can be used in place of a
binomial test
