## Self assessment:

Which of the following describe data in the form of frequencies:

- The number of pregnant women falling into the following categories: non-smoker, light smoker, heavy smoker.
- The percentage of pregnant women falling into the following categories: non-smoker, light smoker, heavy smoker.
- The mean number of cigarettes smoked per day by 20 pregnant women.
- The hair colour (measured as red, brown, black or blonde) of 100 people from Great Britain.
- The number of leaves on 20 geranium plants grown for three weeks in sunlight.
- The number of geranium plants grown in sunlight for three weeks with between 0-10 leaves, 11-20 leaves, or ≥21 leaves.

For each of the following features, say whether it applies to a two-way Chi square test:

- Parametric test.
- Nonparametric test.
- Numbers plugged into the formula for the statistic are frequencies.
- Numbers plugged into the formula for the statistic are percentages.
- Numbers plugged into the formula for the statistic are means and standard deviations.
- Compares an observed frequency distribution with one based on a specified theoretical distribution.
- Should not be used if one or more expected values are zero.
- Should be used with caution if more than one-fifth of the expected values are less than 5.
- Should not be used when an item contributes to more than one cell in the frequency table.
- Used on unrelated data.
- Used for related data.
- Uses a statistic called the 'Pearson Chi-square'.
- Uses a statistic called the 'Likelihood Chi-square'.
- Reject the null hypothesis if the X
^{2}value calculated is less than the critical value of X^{2}looked up in a table.