Binomial Test
The Binomial Test procedure compares the observed frequencies of the two categories of a dichotomous variable to the frequencies that are expected under a binomial distribution with a specified probability parameter. By default, the probability parameter for both groups is 0.5. To change the probabilities, you can enter a test proportion for the first group. The probability for the second group will be 1 minus the specified probability for the first group.
Example. When you toss a dime, the probability of a head equals 1/2. Based on this hypothesis, a dime is tossed 40 times, and the outcomes are recorded (heads or tails). From the binomial test, you might find that 3/4 of the tosses were heads and that the observed significance level is small (0.0027). These results indicate that it is not likely that the probability of a head equals 1/2; the coin is probably biased.
Statistics. Mean, standard deviation, minimum, maximum, number of nonmissing cases, and quartiles.
Binomial Test Data Considerations
Data. The variables that are tested should be numeric and dichotomous. To convert string variables to numeric variables, use the Automatic Recode procedure, which is available on the Transform menu. A dichotomous variable is a variable that can take only two possible values: yes or no, true or false, 0 or 1, and so on. The first value encountered in the dataset defines the first group, and the other value defines the second group. If the variables are not dichotomous, you must specify a cut point. The cut point assigns cases with values that are less than or equal to the cut point to the first group and assigns the rest of the cases to the second group.
Assumptions. Nonparametric tests do not require assumptions about the shape of the underlying distribution. The data are assumed to be a random sample.
To Obtain a Binomial Test
This feature requires the Statistics Base option.
- From the menus choose:
- Select one or more numeric test variables.
- Optionally, click Options for descriptive statistics, quartiles, and control of the treatment of missing data.
This procedure pastes NPAR TESTS command syntax.